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	$214.66	11.868%	$240.1358	$240.14	$240.15	$240.10
Purchase #2	$246.79	11.614%	$275.4522	$275.45	$275.45	$275.50
Purchase #3	$94.73	5.633%	$100.0661	$100.07	$100.05	$100.10
Purchase #4	$154.35	11.187%	$171.6171	$171.62	$171.60	$171.60
Purchase #5	$70.99	9.249%	$77.5559	$77.56	$77.55	$77.60
Purchase #6	$40.42	12.571%	$45.5012	$45.50	$45.50	$45.50
Purchase #7	$63.62	3.548%	$65.8772	$65.88	$65.90	$65.90
7 purchase totals =	$885.56		$976.2055	$976.22	$976.20	$976.30