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	$185.50	13.518%	$210.5759	$210.58	$210.60	$210.60
Purchase #2	$205.63	9.870%	$225.9257	$225.93	$225.95	$225.90
Purchase #3	$226.96	6.521%	$241.7601	$241.76	$241.75	$241.80
Purchase #4	$189.90	10.363%	$209.5793	$209.58	$209.60	$209.60
Purchase #5	$95.27	10.774%	$105.5344	$105.53	$105.55	$105.50
Purchase #6	$247.31	3.765%	$256.6212	$256.62	$256.60	$256.60
Purchase #7	$195.41	5.658%	$206.4663	$206.47	$206.45	$206.50
7 purchase totals =	$1,345.98		$1,456.4629	$1,456.47	$1,456.50	$1,456.50