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	$125.42	3.753%	$130.127	$130.13	$130.15	$130.10
Purchase #2	$148.77	7.800%	$160.3741	$160.37	$160.35	$160.40
Purchase #3	$247.91	4.204%	$258.3321	$258.33	$258.35	$258.30
Purchase #4	$65.54	9.677%	$71.8823	$71.88	$71.90	$71.90
Purchase #5	$186.27	10.683%	$206.1692	$206.17	$206.15	$206.20
Purchase #6	$95.72	3.760%	$99.3191	$99.32	$99.30	$99.30
Purchase #7	$120.77	13.323%	$136.8602	$136.86	$136.85	$136.90
7 purchase totals =	$990.40		$1,063.0640	$1,063.06	$1,063.05	$1,063.10