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	$189.49	11.282%	$210.8683	$210.87	$210.85	$210.90
Purchase #2	$60.32	10.151%	$66.4431	$66.44	$66.45	$66.40
Purchase #3	$137.40	3.865%	$142.7105	$142.71	$142.70	$142.70
Purchase #4	$172.52	10.178%	$190.0791	$190.08	$190.10	$190.10
Purchase #5	$59.98	7.616%	$64.5481	$64.55	$64.55	$64.50
Purchase #6	$148.96	12.405%	$167.4385	$167.44	$167.45	$167.40
Purchase #7	$132.54	13.793%	$150.8212	$150.82	$150.80	$150.80
7 purchase totals =	$901.21		$992.9088	$992.91	$992.90	$992.80