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	$63.82	5.315%	$67.212	$67.21	$67.20	$67.20
Purchase #2	$29.46	7.482%	$31.6642	$31.66	$31.65	$31.70
Purchase #3	$170.54	10.536%	$188.5081	$188.51	$188.50	$188.50
Purchase #4	$99.48	3.539%	$103.0006	$103.00	$103.00	$103.00
Purchase #5	$102.55	4.225%	$106.8827	$106.88	$106.90	$106.90
Purchase #6	$42.87	6.165%	$45.5129	$45.51	$45.50	$45.50
Purchase #7	$11.59	8.259%	$12.5472	$12.55	$12.55	$12.50
7 purchase totals =	$520.31		$555.3277	$555.32	$555.30	$555.30