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	$37.43	9.821%	$41.106	$41.11	$41.10	$41.10
Purchase #2	$34.64	4.368%	$36.1531	$36.15	$36.15	$36.20
Purchase #3	$212.64	11.159%	$236.3685	$236.37	$236.35	$236.40
Purchase #4	$141.37	7.371%	$151.7904	$151.79	$151.80	$151.80
Purchase #5	$14.51	6.518%	$15.4558	$15.46	$15.45	$15.50
Purchase #6	$62.33	12.588%	$70.1761	$70.18	$70.20	$70.20
Purchase #7	$92.32	7.805%	$99.5256	$99.53	$99.55	$99.50
7 purchase totals =	$595.24		$650.5755	$650.59	$650.60	$650.70