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	$49.81	6.300%	$52.948	$52.95	$52.95	$52.90
Purchase #2	$46.88	8.377%	$50.8071	$50.81	$50.80	$50.80
Purchase #3	$236.44	11.579%	$263.8174	$263.82	$263.80	$263.80
Purchase #4	$37.46	8.468%	$40.6321	$40.63	$40.65	$40.60
Purchase #5	$103.40	6.846%	$110.4788	$110.48	$110.50	$110.50
Purchase #6	$133.59	13.373%	$151.455	$151.46	$151.45	$151.50
Purchase #7	$168.65	7.246%	$180.8704	$180.87	$180.85	$180.90
7 purchase totals =	$776.23		$851.0088	$851.02	$851.00	$851.00