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	$61.73	5.436%	$65.0856	$65.09	$65.10	$65.10
Purchase #2	$91.37	4.546%	$95.5237	$95.52	$95.50	$95.50
Purchase #3	$36.82	7.765%	$39.6791	$39.68	$39.70	$39.70
Purchase #4	$76.86	6.858%	$82.1311	$82.13	$82.15	$82.10
Purchase #5	$19.41	8.401%	$21.0406	$21.04	$21.05	$21.00
Purchase #6	$74.69	10.521%	$82.5481	$82.55	$82.55	$82.50
Purchase #7	$53.84	12.620%	$60.6346	$60.63	$60.65	$60.60
7 purchase totals =	$414.72		$446.6428	$446.64	$446.70	$446.50