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	$142.96	6.348%	$152.0351	$152.04	$152.05	$152.00
Purchase #2	$93.47	6.566%	$99.6072	$99.61	$99.60	$99.60
Purchase #3	$149.50	5.864%	$158.2667	$158.27	$158.25	$158.30
Purchase #4	$111.92	12.477%	$125.8843	$125.88	$125.90	$125.90
Purchase #5	$10.29	7.767%	$11.0892	$11.09	$11.10	$11.10
Purchase #6	$148.44	6.859%	$158.6215	$158.62	$158.60	$158.60
Purchase #7	$55.91	11.594%	$62.3922	$62.39	$62.40	$62.40
7 purchase totals =	$712.49		$767.8962	$767.90	$767.90	$767.90