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	$130.29	12.288%	$146.3	$146.30	$146.30	$146.30
Purchase #2	$201.27	3.405%	$208.1232	$208.12	$208.10	$208.10
Purchase #3	$86.26	5.168%	$90.7179	$90.72	$90.70	$90.70
Purchase #4	$146.95	5.119%	$154.4724	$154.47	$154.45	$154.50
Purchase #5	$104.50	6.565%	$111.3604	$111.36	$111.35	$111.40
Purchase #6	$26.51	13.235%	$30.0186	$30.02	$30.00	$30.00
Purchase #7	$112.42	10.788%	$124.5479	$124.55	$124.55	$124.50
7 purchase totals =	$808.20		$865.5404	$865.54	$865.45	$865.50