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	$53.58	10.391%	$59.1475	$59.15	$59.15	$59.10
Purchase #2	$27.38	4.690%	$28.6641	$28.66	$28.65	$28.70
Purchase #3	$69.91	11.803%	$78.1615	$78.16	$78.15	$78.20
Purchase #4	$60.29	13.151%	$68.2187	$68.22	$68.20	$68.20
Purchase #5	$56.57	5.402%	$59.6259	$59.63	$59.65	$59.60
Purchase #6	$6.72	3.634%	$6.9642	$6.96	$6.95	$7.00
Purchase #7	$163.65	11.523%	$182.5074	$182.51	$182.50	$182.50
7 purchase totals =	$438.10		$483.2893	$483.29	$483.25	$483.30