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	$146.32	3.815%	$151.9021	$151.90	$151.90	$151.90
Purchase #2	$62.42	8.119%	$67.4879	$67.49	$67.50	$67.50
Purchase #3	$65.65	10.282%	$72.4001	$72.40	$72.40	$72.40
Purchase #4	$100.41	6.432%	$106.8684	$106.87	$106.85	$106.90
Purchase #5	$244.49	13.263%	$276.9167	$276.92	$276.90	$276.90
Purchase #6	$35.83	5.267%	$37.7172	$37.72	$37.70	$37.70
Purchase #7	$158.57	11.674%	$177.0815	$177.08	$177.10	$177.10
7 purchase totals =	$813.69		$890.3739	$890.38	$890.35	$890.40