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	$167.51	8.225%	$181.2877	$181.29	$181.30	$181.30
Purchase #2	$194.77	9.103%	$212.4999	$212.50	$212.50	$212.50
Purchase #3	$89.82	9.695%	$98.528	$98.53	$98.55	$98.50
Purchase #4	$36.93	13.869%	$42.0518	$42.05	$42.05	$42.10
Purchase #5	$167.94	12.593%	$189.0887	$189.09	$189.10	$189.10
Purchase #6	$161.67	11.622%	$180.4593	$180.46	$180.45	$180.50
Purchase #7	$242.88	3.517%	$251.4221	$251.42	$251.40	$251.40
7 purchase totals =	$1,061.52		$1,155.3375	$1,155.34	$1,155.35	$1,155.40