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	$117.31	10.348%	$129.4492	$129.45	$129.45	$129.40
Purchase #2	$78.41	12.725%	$88.3877	$88.39	$88.40	$88.40
Purchase #3	$242.27	7.661%	$260.8303	$260.83	$260.85	$260.80
Purchase #4	$244.64	4.849%	$256.5026	$256.50	$256.50	$256.50
Purchase #5	$86.36	5.498%	$91.1081	$91.11	$91.10	$91.10
Purchase #6	$240.51	4.405%	$251.1045	$251.10	$251.10	$251.10
Purchase #7	$25.51	10.658%	$28.2289	$28.23	$28.25	$28.20
7 purchase totals =	$1,035.01		$1,105.6113	$1,105.61	$1,105.65	$1,105.50