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	$98.84	12.801%	$111.4925	$111.49	$111.50	$111.50
Purchase #2	$122.47	6.852%	$130.8616	$130.86	$130.85	$130.90
Purchase #3	$9.63	9.256%	$10.5214	$10.52	$10.50	$10.50
Purchase #4	$56.41	5.175%	$59.3292	$59.33	$59.35	$59.30
Purchase #5	$169.30	3.773%	$175.6877	$175.69	$175.70	$175.70
Purchase #6	$196.45	9.652%	$215.4114	$215.41	$215.40	$215.40
Purchase #7	$93.53	6.609%	$99.7114	$99.71	$99.70	$99.70
7 purchase totals =	$746.63		$803.0152	$803.01	$803.00	$803.00