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	$155.46	13.321%	$176.1688	$176.17	$176.15	$176.20
Purchase #2	$48.42	12.210%	$54.3321	$54.33	$54.35	$54.30
Purchase #3	$84.42	7.444%	$90.7042	$90.70	$90.70	$90.70
Purchase #4	$45.35	4.328%	$47.3127	$47.31	$47.30	$47.30
Purchase #5	$66.97	7.299%	$71.8581	$71.86	$71.85	$71.90
Purchase #6	$216.34	3.349%	$223.5852	$223.59	$223.60	$223.60
Purchase #7	$82.56	8.858%	$89.8732	$89.87	$89.85	$89.90
7 purchase totals =	$699.52		$753.8343	$753.83	$753.80	$753.90