Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$172.72	10.585%	$191.0024	$191.00	$191.00	$191.00
Purchase #2	$197.89	11.479%	$220.6058	$220.61	$220.60	$220.60
Purchase #3	$165.74	5.240%	$174.4248	$174.42	$174.40	$174.40
Purchase #4	$188.84	13.412%	$214.1672	$214.17	$214.15	$214.20
Purchase #5	$106.57	5.150%	$112.0584	$112.06	$112.05	$112.10
Purchase #6	$163.66	10.760%	$181.2698	$181.27	$181.25	$181.30
Purchase #7	$161.40	6.429%	$171.7764	$171.78	$171.80	$171.80
7 purchase totals =	$1,156.82		$1,265.3048	$1,265.31	$1,265.25	$1,265.40