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	$187.72	8.759%	$204.1624	$204.16	$204.15	$204.20
Purchase #2	$20.76	3.119%	$21.4075	$21.41	$21.40	$21.40
Purchase #3	$49.50	10.417%	$54.6564	$54.66	$54.65	$54.70
Purchase #4	$80.95	5.356%	$85.2857	$85.29	$85.30	$85.30
Purchase #5	$124.40	12.118%	$139.4748	$139.47	$139.45	$139.50
Purchase #6	$19.87	12.206%	$22.2953	$22.30	$22.30	$22.30
Purchase #7	$7.32	8.398%	$7.9347	$7.93	$7.95	$7.90
7 purchase totals =	$490.52		$535.2168	$535.22	$535.20	$535.30