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	$179.52	6.322%	$190.8693	$190.87	$190.85	$190.90
Purchase #2	$221.96	13.430%	$251.7692	$251.77	$251.75	$251.80
Purchase #3	$33.55	12.552%	$37.7612	$37.76	$37.75	$37.80
Purchase #4	$231.66	8.566%	$251.504	$251.50	$251.50	$251.50
Purchase #5	$182.73	7.286%	$196.0437	$196.04	$196.05	$196.00
Purchase #6	$90.44	10.342%	$99.7933	$99.79	$99.80	$99.80
Purchase #7	$218.63	8.188%	$236.5314	$236.53	$236.55	$236.50
7 purchase totals =	$1,158.49		$1,264.2721	$1,264.26	$1,264.25	$1,264.30