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	$200.88	5.714%	$212.3583	$212.36	$212.35	$212.40
Purchase #2	$89.30	7.362%	$95.8743	$95.87	$95.85	$95.90
Purchase #3	$158.31	8.715%	$172.1067	$172.11	$172.10	$172.10
Purchase #4	$32.57	9.805%	$35.7635	$35.76	$35.75	$35.80
Purchase #5	$82.59	11.859%	$92.3843	$92.38	$92.40	$92.40
Purchase #6	$244.25	8.150%	$264.1564	$264.16	$264.15	$264.20
Purchase #7	$64.74	7.791%	$69.7839	$69.78	$69.80	$69.80
7 purchase totals =	$872.64		$942.4274	$942.42	$942.40	$942.60