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	$44.33	3.576%	$45.9152	$45.92	$45.90	$45.90
Purchase #2	$138.72	5.730%	$146.6687	$146.67	$146.65	$146.70
Purchase #3	$90.47	4.827%	$94.837	$94.84	$94.85	$94.80
Purchase #4	$47.40	13.279%	$53.6942	$53.69	$53.70	$53.70
Purchase #5	$35.59	11.183%	$39.57	$39.57	$39.55	$39.60
Purchase #6	$34.36	13.546%	$39.0144	$39.01	$39.00	$39.00
Purchase #7	$59.68	6.366%	$63.4792	$63.48	$63.50	$63.50
7 purchase totals =	$450.55		$483.1787	$483.18	$483.15	$483.20