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	$233.53	9.817%	$256.4556	$256.46	$256.45	$256.50
Purchase #2	$41.86	9.217%	$45.7182	$45.72	$45.70	$45.70
Purchase #3	$195.86	7.367%	$210.289	$210.29	$210.30	$210.30
Purchase #4	$162.91	3.144%	$168.0319	$168.03	$168.05	$168.00
Purchase #5	$22.26	10.830%	$24.6708	$24.67	$24.65	$24.70
Purchase #6	$182.35	4.112%	$189.8482	$189.85	$189.85	$189.80
Purchase #7	$174.39	6.757%	$186.1735	$186.17	$186.15	$186.20
7 purchase totals =	$1,013.16		$1,081.1872	$1,081.19	$1,081.15	$1,081.20