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	$153.97	6.649%	$164.2075	$164.21	$164.20	$164.20
Purchase #2	$56.96	4.821%	$59.706	$59.71	$59.70	$59.70
Purchase #3	$53.74	10.799%	$59.5434	$59.54	$59.55	$59.50
Purchase #4	$10.43	3.300%	$10.7742	$10.77	$10.75	$10.80
Purchase #5	$82.76	12.789%	$93.3442	$93.34	$93.35	$93.30
Purchase #6	$52.53	8.125%	$56.7981	$56.80	$56.80	$56.80
Purchase #7	$76.26	9.847%	$83.7693	$83.77	$83.75	$83.80
7 purchase totals =	$486.65		$528.1427	$528.14	$528.10	$528.10