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	$168.40	9.687%	$184.7129	$184.71	$184.70	$184.70
Purchase #2	$56.38	10.226%	$62.1454	$62.15	$62.15	$62.10
Purchase #3	$26.27	7.282%	$28.183	$28.18	$28.20	$28.20
Purchase #4	$102.28	11.372%	$113.9113	$113.91	$113.90	$113.90
Purchase #5	$157.33	7.808%	$169.6143	$169.61	$169.60	$169.60
Purchase #6	$62.63	13.569%	$71.1283	$71.13	$71.15	$71.10
Purchase #7	$105.54	5.715%	$111.5716	$111.57	$111.55	$111.60
7 purchase totals =	$678.83		$741.2668	$741.26	$741.25	$741.20