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	$66.78	7.669%	$71.9014	$71.90	$71.90	$71.90
Purchase #2	$118.49	8.541%	$128.6102	$128.61	$128.60	$128.60
Purchase #3	$217.53	13.499%	$246.8944	$246.89	$246.90	$246.90
Purchase #4	$181.77	5.400%	$191.5856	$191.59	$191.60	$191.60
Purchase #5	$227.82	10.155%	$250.9551	$250.96	$250.95	$251.00
Purchase #6	$131.57	9.844%	$144.5218	$144.52	$144.50	$144.50
Purchase #7	$175.87	8.785%	$191.3202	$191.32	$191.30	$191.30
7 purchase totals =	$1,119.83		$1,225.7887	$1,225.79	$1,225.75	$1,225.80