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	$118.85	11.141%	$132.0911	$132.09	$132.10	$132.10
Purchase #2	$218.34	5.762%	$230.9208	$230.92	$230.90	$230.90
Purchase #3	$203.65	9.152%	$222.288	$222.29	$222.30	$222.30
Purchase #4	$36.75	5.512%	$38.7757	$38.78	$38.80	$38.80
Purchase #5	$136.43	3.594%	$141.3333	$141.33	$141.35	$141.30
Purchase #6	$48.87	10.250%	$53.8792	$53.88	$53.90	$53.90
Purchase #7	$248.27	11.791%	$277.5435	$277.54	$277.55	$277.50
7 purchase totals =	$1,011.16		$1,096.8316	$1,096.83	$1,096.90	$1,096.80