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	$180.29	6.430%	$191.8826	$191.88	$191.90	$191.90
Purchase #2	$11.89	3.707%	$12.3308	$12.33	$12.35	$12.30
Purchase #3	$60.86	10.805%	$67.4359	$67.44	$67.45	$67.40
Purchase #4	$92.83	5.335%	$97.7825	$97.78	$97.80	$97.80
Purchase #5	$179.31	3.316%	$185.2559	$185.26	$185.25	$185.30
Purchase #6	$239.69	12.208%	$268.9514	$268.95	$268.95	$269.00
Purchase #7	$42.53	10.676%	$47.0705	$47.07	$47.05	$47.10
7 purchase totals =	$807.40		$870.7096	$870.71	$870.75	$870.80