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	$83.42	8.549%	$90.5516	$90.55	$90.55	$90.60
Purchase #2	$150.74	8.122%	$162.9831	$162.98	$163.00	$163.00
Purchase #3	$96.66	4.390%	$100.9034	$100.90	$100.90	$100.90
Purchase #4	$112.43	9.446%	$123.0501	$123.05	$123.05	$123.10
Purchase #5	$143.39	12.461%	$161.2578	$161.26	$161.25	$161.30
Purchase #6	$205.90	6.424%	$219.127	$219.13	$219.15	$219.10
Purchase #7	$229.65	6.812%	$245.2938	$245.29	$245.30	$245.30
7 purchase totals =	$1,022.19		$1,103.1668	$1,103.16	$1,103.20	$1,103.30