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	$200.98	5.562%	$212.1585	$212.16	$212.15	$212.20
Purchase #2	$83.88	5.360%	$88.376	$88.38	$88.40	$88.40
Purchase #3	$145.81	4.342%	$152.1411	$152.14	$152.15	$152.10
Purchase #4	$37.58	10.672%	$41.5905	$41.59	$41.60	$41.60
Purchase #5	$71.81	9.513%	$78.6413	$78.64	$78.65	$78.60
Purchase #6	$141.59	4.332%	$147.7237	$147.72	$147.70	$147.70
Purchase #7	$30.97	7.272%	$33.2221	$33.22	$33.20	$33.20
7 purchase totals =	$712.62		$753.8532	$753.85	$753.85	$753.80