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	$45.73	5.231%	$48.1221	$48.12	$48.10	$48.10
Purchase #2	$237.39	5.365%	$250.126	$250.13	$250.15	$250.10
Purchase #3	$7.54	7.647%	$8.1166	$8.12	$8.10	$8.10
Purchase #4	$223.63	3.494%	$231.4436	$231.44	$231.45	$231.40
Purchase #5	$122.31	4.124%	$127.3541	$127.35	$127.35	$127.40
Purchase #6	$184.83	10.547%	$204.324	$204.32	$204.30	$204.30
Purchase #7	$199.26	12.184%	$223.5378	$223.54	$223.55	$223.50
7 purchase totals =	$1,020.69		$1,093.0242	$1,093.02	$1,093.00	$1,092.90