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	$139.91	9.321%	$152.951	$152.95	$152.95	$153.00
Purchase #2	$27.76	13.282%	$31.4471	$31.45	$31.45	$31.40
Purchase #3	$144.77	5.292%	$152.4312	$152.43	$152.45	$152.40
Purchase #4	$79.82	11.143%	$88.7143	$88.71	$88.70	$88.70
Purchase #5	$136.51	4.485%	$142.6325	$142.63	$142.65	$142.60
Purchase #6	$101.37	9.620%	$111.1218	$111.12	$111.10	$111.10
Purchase #7	$249.82	7.133%	$267.6397	$267.64	$267.65	$267.60
7 purchase totals =	$879.96		$946.9376	$946.93	$946.95	$946.80