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	$148.71	11.109%	$165.2302	$165.23	$165.25	$165.20
Purchase #2	$104.75	6.552%	$111.6132	$111.61	$111.60	$111.60
Purchase #3	$65.93	8.199%	$71.3356	$71.34	$71.35	$71.30
Purchase #4	$143.98	5.377%	$151.7218	$151.72	$151.70	$151.70
Purchase #5	$35.69	5.357%	$37.6019	$37.60	$37.60	$37.60
Purchase #6	$92.96	10.824%	$103.022	$103.02	$103.00	$103.00
Purchase #7	$247.81	8.412%	$268.6558	$268.66	$268.65	$268.70
7 purchase totals =	$839.83		$909.1805	$909.18	$909.15	$909.10