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	$95.91	5.131%	$100.8311	$100.83	$100.85	$100.80
Purchase #2	$27.35	5.632%	$28.8904	$28.89	$28.90	$28.90
Purchase #3	$117.64	6.679%	$125.4972	$125.50	$125.50	$125.50
Purchase #4	$53.87	11.294%	$59.9541	$59.95	$59.95	$60.00
Purchase #5	$55.45	3.448%	$57.3619	$57.36	$57.35	$57.40
Purchase #6	$11.59	4.479%	$12.1091	$12.11	$12.10	$12.10
Purchase #7	$195.58	8.282%	$211.7779	$211.78	$211.80	$211.80
7 purchase totals =	$557.39		$596.4217	$596.42	$596.45	$596.50