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	$69.78	4.318%	$72.7931	$72.79	$72.80	$72.80
Purchase #2	$230.45	5.639%	$243.4451	$243.45	$243.45	$243.40
Purchase #3	$226.74	8.195%	$245.3213	$245.32	$245.30	$245.30
Purchase #4	$108.52	13.827%	$123.5251	$123.53	$123.55	$123.50
Purchase #5	$15.33	9.659%	$16.8107	$16.81	$16.80	$16.80
Purchase #6	$159.77	7.786%	$172.2097	$172.21	$172.20	$172.20
Purchase #7	$84.57	5.593%	$89.3	$89.30	$89.30	$89.30
7 purchase totals =	$895.16		$963.4050	$963.41	$963.40	$963.30