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	$226.50	3.203%	$233.7548	$233.75	$233.75	$233.80
Purchase #2	$73.54	4.529%	$76.8706	$76.87	$76.85	$76.90
Purchase #3	$99.99	11.343%	$111.3319	$111.33	$111.35	$111.30
Purchase #4	$72.51	11.579%	$80.9059	$80.91	$80.90	$80.90
Purchase #5	$224.61	9.675%	$246.341	$246.34	$246.35	$246.30
Purchase #6	$70.89	8.164%	$76.6775	$76.68	$76.70	$76.70
Purchase #7	$54.68	12.191%	$61.346	$61.35	$61.35	$61.30
7 purchase totals =	$822.72		$887.2277	$887.23	$887.25	$887.20