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	$88.47	9.344%	$96.7366	$96.74	$96.75	$96.70
Purchase #2	$89.26	3.462%	$92.3502	$92.35	$92.35	$92.40
Purchase #3	$77.86	9.347%	$85.1376	$85.14	$85.15	$85.10
Purchase #4	$32.49	10.275%	$35.8283	$35.83	$35.85	$35.80
Purchase #5	$158.35	7.714%	$170.5651	$170.57	$170.55	$170.60
Purchase #6	$203.32	13.402%	$230.5689	$230.57	$230.55	$230.60
Purchase #7	$78.81	8.375%	$85.4103	$85.41	$85.40	$85.40
7 purchase totals =	$728.56		$796.5970	$796.61	$796.60	$796.60