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	$69.44	9.116%	$75.7702	$75.77	$75.75	$75.80
Purchase #2	$55.53	13.371%	$62.9549	$62.95	$62.95	$63.00
Purchase #3	$121.69	12.632%	$137.0619	$137.06	$137.05	$137.10
Purchase #4	$32.31	8.393%	$35.0218	$35.02	$35.00	$35.00
Purchase #5	$235.67	12.167%	$264.344	$264.34	$264.35	$264.30
Purchase #6	$147.40	10.271%	$162.5395	$162.54	$162.55	$162.50
Purchase #7	$244.50	12.405%	$274.8302	$274.83	$274.85	$274.80
7 purchase totals =	$906.54		$1,012.5225	$1,012.51	$1,012.50	$1,012.50