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	$191.99	9.402%	$210.0409	$210.04	$210.05	$210.00
Purchase #2	$59.31	12.733%	$66.8619	$66.86	$66.85	$66.90
Purchase #3	$56.30	11.703%	$62.8888	$62.89	$62.90	$62.90
Purchase #4	$150.96	9.584%	$165.428	$165.43	$165.45	$165.40
Purchase #5	$94.80	7.114%	$101.5441	$101.54	$101.55	$101.50
Purchase #6	$145.68	3.689%	$151.0541	$151.05	$151.05	$151.10
Purchase #7	$50.40	12.334%	$56.6163	$56.62	$56.60	$56.60
7 purchase totals =	$749.44		$814.4341	$814.43	$814.45	$814.40