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	$221.45	13.554%	$251.4653	$251.47	$251.45	$251.50
Purchase #2	$83.80	9.661%	$91.8959	$91.90	$91.90	$91.90
Purchase #3	$44.37	7.638%	$47.759	$47.76	$47.75	$47.80
Purchase #4	$247.33	7.472%	$265.8105	$265.81	$265.80	$265.80
Purchase #5	$99.64	6.197%	$105.8147	$105.81	$105.80	$105.80
Purchase #6	$229.89	5.592%	$242.7454	$242.75	$242.75	$242.70
Purchase #7	$49.43	10.849%	$54.7927	$54.79	$54.80	$54.80
7 purchase totals =	$975.91		$1,060.2835	$1,060.29	$1,060.25	$1,060.30