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	$153.95	8.459%	$166.9726	$166.97	$166.95	$167.00
Purchase #2	$57.70	13.778%	$65.6499	$65.65	$65.65	$65.60
Purchase #3	$140.36	4.389%	$146.5204	$146.52	$146.50	$146.50
Purchase #4	$59.47	4.375%	$62.0718	$62.07	$62.05	$62.10
Purchase #5	$93.70	7.324%	$100.5626	$100.56	$100.55	$100.60
Purchase #6	$160.79	3.402%	$166.2601	$166.26	$166.25	$166.30
Purchase #7	$178.49	6.186%	$189.5314	$189.53	$189.55	$189.50
7 purchase totals =	$844.46		$897.5688	$897.56	$897.50	$897.60