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	$183.81	4.583%	$192.234	$192.23	$192.25	$192.20
Purchase #2	$120.93	4.700%	$126.6137	$126.61	$126.60	$126.60
Purchase #3	$29.47	12.654%	$33.1991	$33.20	$33.20	$33.20
Purchase #4	$59.93	4.199%	$62.4465	$62.45	$62.45	$62.40
Purchase #5	$30.44	9.373%	$33.2931	$33.29	$33.30	$33.30
Purchase #6	$148.88	10.313%	$164.234	$164.23	$164.25	$164.20
Purchase #7	$223.85	8.733%	$243.3988	$243.40	$243.40	$243.40
7 purchase totals =	$797.31		$855.4192	$855.41	$855.45	$855.30