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	$208.59	4.228%	$217.4092	$217.41	$217.40	$217.40
Purchase #2	$84.89	5.520%	$89.5759	$89.58	$89.60	$89.60
Purchase #3	$69.33	10.652%	$76.715	$76.72	$76.70	$76.70
Purchase #4	$33.57	10.419%	$37.0677	$37.07	$37.05	$37.10
Purchase #5	$110.55	11.836%	$123.6347	$123.63	$123.65	$123.60
Purchase #6	$74.42	4.310%	$77.6275	$77.63	$77.65	$77.60
Purchase #7	$29.73	7.181%	$31.8649	$31.86	$31.85	$31.90
7 purchase totals =	$611.08		$653.8949	$653.90	$653.90	$653.90