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	$125.34	12.604%	$141.1379	$141.14	$141.15	$141.10
Purchase #2	$141.86	8.535%	$153.9678	$153.97	$153.95	$154.00
Purchase #3	$62.86	13.758%	$71.5083	$71.51	$71.50	$71.50
Purchase #4	$53.56	6.144%	$56.8507	$56.85	$56.85	$56.90
Purchase #5	$238.58	10.492%	$263.6118	$263.61	$263.60	$263.60
Purchase #6	$126.81	8.304%	$137.3403	$137.34	$137.35	$137.30
Purchase #7	$153.94	9.202%	$168.1056	$168.11	$168.10	$168.10
7 purchase totals =	$902.95		$992.5224	$992.53	$992.50	$992.50