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	$13.40	8.635%	$14.5571	$14.56	$14.55	$14.60
Purchase #2	$149.86	3.408%	$154.9672	$154.97	$154.95	$155.00
Purchase #3	$191.96	13.123%	$217.1509	$217.15	$217.15	$217.20
Purchase #4	$157.25	3.217%	$162.3087	$162.31	$162.30	$162.30
Purchase #5	$35.80	5.753%	$37.8596	$37.86	$37.85	$37.90
Purchase #6	$216.37	3.853%	$224.7067	$224.71	$224.70	$224.70
Purchase #7	$239.28	4.610%	$250.3108	$250.31	$250.30	$250.30
7 purchase totals =	$1,003.92		$1,061.8610	$1,061.87	$1,061.80	$1,062.00