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	$29.43	12.865%	$33.2162	$33.22	$33.20	$33.20
Purchase #2	$169.26	9.471%	$185.2906	$185.29	$185.30	$185.30
Purchase #3	$22.63	9.662%	$24.8165	$24.82	$24.80	$24.80
Purchase #4	$201.74	10.507%	$222.9368	$222.94	$222.95	$222.90
Purchase #5	$181.59	7.865%	$195.8721	$195.87	$195.85	$195.90
Purchase #6	$6.60	13.576%	$7.496	$7.50	$7.50	$7.50
Purchase #7	$52.45	4.383%	$54.7489	$54.75	$54.75	$54.70
7 purchase totals =	$663.70		$724.3771	$724.39	$724.35	$724.30