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	$232.76	8.802%	$253.2475	$253.25	$253.25	$253.20
Purchase #2	$219.69	10.684%	$243.1617	$243.16	$243.15	$243.20
Purchase #3	$14.50	6.758%	$15.4799	$15.48	$15.50	$15.50
Purchase #4	$242.75	5.143%	$255.2346	$255.23	$255.25	$255.20
Purchase #5	$243.74	12.835%	$275.024	$275.02	$275.00	$275.00
Purchase #6	$240.61	9.224%	$262.8039	$262.80	$262.80	$262.80
Purchase #7	$72.76	12.634%	$81.9525	$81.95	$81.95	$82.00
7 purchase totals =	$1,266.81		$1,386.9041	$1,386.89	$1,386.90	$1,386.90