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	$40.89	12.622%	$46.0511	$46.05	$46.05	$46.10
Purchase #2	$90.67	4.267%	$94.5389	$94.54	$94.55	$94.50
Purchase #3	$16.63	10.250%	$18.3346	$18.33	$18.35	$18.30
Purchase #4	$110.96	13.501%	$125.9407	$125.94	$125.95	$125.90
Purchase #5	$95.83	9.620%	$105.0488	$105.05	$105.05	$105.00
Purchase #6	$82.37	8.537%	$89.4019	$89.40	$89.40	$89.40
Purchase #7	$49.34	9.788%	$54.1694	$54.17	$54.15	$54.20
7 purchase totals =	$486.69		$533.4854	$533.48	$533.50	$533.40