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	$143.68	3.334%	$148.4703	$148.47	$148.45	$148.50
Purchase #2	$145.62	8.536%	$158.0501	$158.05	$158.05	$158.10
Purchase #3	$139.57	11.165%	$155.153	$155.15	$155.15	$155.20
Purchase #4	$106.96	12.740%	$120.5867	$120.59	$120.60	$120.60
Purchase #5	$16.50	11.708%	$18.4318	$18.43	$18.45	$18.40
Purchase #6	$176.55	11.717%	$197.2364	$197.24	$197.25	$197.20
Purchase #7	$91.81	8.802%	$99.8911	$99.89	$99.90	$99.90
7 purchase totals =	$820.69		$897.8194	$897.82	$897.85	$897.90