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	$46.40	4.718%	$48.5892	$48.59	$48.60	$48.60
Purchase #2	$106.98	8.627%	$116.2092	$116.21	$116.20	$116.20
Purchase #3	$100.78	5.868%	$106.6938	$106.69	$106.70	$106.70
Purchase #4	$45.35	9.102%	$49.4778	$49.48	$49.50	$49.50
Purchase #5	$88.96	13.139%	$100.6485	$100.65	$100.65	$100.60
Purchase #6	$92.73	6.714%	$98.9559	$98.96	$98.95	$99.00
Purchase #7	$92.67	8.516%	$100.5618	$100.56	$100.55	$100.60
7 purchase totals =	$573.87		$621.1362	$621.14	$621.15	$621.20