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	$32.29	11.216%	$35.9116	$35.91	$35.90	$35.90
Purchase #2	$20.43	11.212%	$22.7206	$22.72	$22.70	$22.70
Purchase #3	$94.58	11.773%	$105.7149	$105.71	$105.70	$105.70
Purchase #4	$222.69	10.293%	$245.6115	$245.61	$245.60	$245.60
Purchase #5	$78.82	7.481%	$84.7165	$84.72	$84.70	$84.70
Purchase #6	$129.78	13.166%	$146.8668	$146.87	$146.85	$146.90
Purchase #7	$140.45	5.316%	$147.9163	$147.92	$147.90	$147.90
7 purchase totals =	$719.04		$789.4582	$789.46	$789.35	$789.40