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	$155.54	10.405%	$171.7239	$171.72	$171.70	$171.70
Purchase #2	$139.90	8.654%	$152.0069	$152.01	$152.00	$152.00
Purchase #3	$216.81	13.219%	$245.4701	$245.47	$245.45	$245.50
Purchase #4	$71.60	11.695%	$79.9736	$79.97	$79.95	$80.00
Purchase #5	$232.25	7.452%	$249.5573	$249.56	$249.55	$249.60
Purchase #6	$38.93	7.140%	$41.7096	$41.71	$41.70	$41.70
Purchase #7	$149.72	3.575%	$155.0725	$155.07	$155.05	$155.10
7 purchase totals =	$1,004.75		$1,095.5139	$1,095.51	$1,095.40	$1,095.60