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	$150.48	10.669%	$166.5347	$166.53	$166.55	$166.50
Purchase #2	$90.67	9.701%	$99.4659	$99.47	$99.45	$99.50
Purchase #3	$221.30	4.526%	$231.316	$231.32	$231.30	$231.30
Purchase #4	$208.48	13.119%	$235.8305	$235.83	$235.85	$235.80
Purchase #5	$208.43	13.364%	$236.2846	$236.28	$236.30	$236.30
Purchase #6	$142.29	3.390%	$147.1136	$147.11	$147.10	$147.10
Purchase #7	$32.45	9.695%	$35.596	$35.60	$35.60	$35.60
7 purchase totals =	$1,054.10		$1,152.1413	$1,152.14	$1,152.15	$1,152.10