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	$64.57	10.686%	$71.47	$71.47	$71.45	$71.50
Purchase #2	$109.55	13.678%	$124.5342	$124.53	$124.55	$124.50
Purchase #3	$169.58	12.576%	$190.9064	$190.91	$190.90	$190.90
Purchase #4	$198.77	3.189%	$205.1088	$205.11	$205.10	$205.10
Purchase #5	$46.84	13.204%	$53.0248	$53.02	$53.00	$53.00
Purchase #6	$62.44	8.494%	$67.7437	$67.74	$67.75	$67.70
Purchase #7	$39.43	5.137%	$41.4555	$41.46	$41.45	$41.50
7 purchase totals =	$691.18		$754.2434	$754.24	$754.20	$754.20