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	$158.59	7.792%	$170.9473	$170.95	$170.95	$170.90
Purchase #2	$57.63	6.840%	$61.5719	$61.57	$61.55	$61.60
Purchase #3	$138.93	11.710%	$155.1987	$155.20	$155.20	$155.20
Purchase #4	$231.57	9.863%	$254.4097	$254.41	$254.40	$254.40
Purchase #5	$153.96	9.602%	$168.7432	$168.74	$168.75	$168.70
Purchase #6	$151.64	8.782%	$164.957	$164.96	$164.95	$165.00
Purchase #7	$114.37	7.846%	$123.3435	$123.34	$123.35	$123.30
7 purchase totals =	$1,006.69		$1,099.1713	$1,099.17	$1,099.15	$1,099.10