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	$190.56	9.228%	$208.1449	$208.14	$208.15	$208.10
Purchase #2	$203.70	9.557%	$223.1676	$223.17	$223.15	$223.20
Purchase #3	$15.89	5.795%	$16.8108	$16.81	$16.80	$16.80
Purchase #4	$106.76	12.485%	$120.089	$120.09	$120.10	$120.10
Purchase #5	$31.37	13.431%	$35.5833	$35.58	$35.60	$35.60
Purchase #6	$95.41	5.773%	$100.918	$100.92	$100.90	$100.90
Purchase #7	$247.76	6.675%	$264.298	$264.30	$264.30	$264.30
7 purchase totals =	$891.45		$969.0116	$969.01	$969.00	$969.00