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	$180.66	7.729%	$194.6232	$194.62	$194.60	$194.60
Purchase #2	$18.51	11.440%	$20.6275	$20.63	$20.65	$20.60
Purchase #3	$225.50	8.665%	$245.0396	$245.04	$245.05	$245.00
Purchase #4	$30.76	4.865%	$32.2565	$32.26	$32.25	$32.30
Purchase #5	$223.95	13.827%	$254.9156	$254.92	$254.90	$254.90
Purchase #6	$103.85	7.577%	$111.7187	$111.72	$111.70	$111.70
Purchase #7	$155.82	12.730%	$175.6559	$175.66	$175.65	$175.70
7 purchase totals =	$939.05		$1,034.8370	$1,034.85	$1,034.80	$1,034.80