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	$105.70	5.715%	$111.7408	$111.74	$111.75	$111.70
Purchase #2	$176.98	7.198%	$189.719	$189.72	$189.70	$189.70
Purchase #3	$16.86	11.598%	$18.8154	$18.82	$18.80	$18.80
Purchase #4	$247.79	10.709%	$274.3258	$274.33	$274.35	$274.30
Purchase #5	$63.73	13.530%	$72.3527	$72.35	$72.35	$72.40
Purchase #6	$224.38	12.196%	$251.7454	$251.75	$251.75	$251.70
Purchase #7	$85.36	8.622%	$92.7197	$92.72	$92.70	$92.70
7 purchase totals =	$920.80		$1,011.4188	$1,011.43	$1,011.40	$1,011.30