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	$55.43	4.182%	$57.7481	$57.75	$57.75	$57.70
Purchase #2	$94.85	4.852%	$99.4521	$99.45	$99.45	$99.50
Purchase #3	$16.65	13.690%	$18.9294	$18.93	$18.95	$18.90
Purchase #4	$228.35	8.778%	$248.3946	$248.39	$248.40	$248.40
Purchase #5	$145.73	3.602%	$150.9792	$150.98	$151.00	$151.00
Purchase #6	$47.59	4.715%	$49.8339	$49.83	$49.85	$49.80
Purchase #7	$220.31	4.160%	$229.4749	$229.47	$229.45	$229.50
7 purchase totals =	$808.91		$854.8122	$854.80	$854.85	$854.80