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	$118.53	8.381%	$128.464	$128.46	$128.45	$128.50
Purchase #2	$208.56	11.166%	$231.8478	$231.85	$231.85	$231.80
Purchase #3	$169.76	6.790%	$181.2867	$181.29	$181.30	$181.30
Purchase #4	$138.66	6.346%	$147.4594	$147.46	$147.45	$147.50
Purchase #5	$161.81	3.518%	$167.5025	$167.50	$167.50	$167.50
Purchase #6	$111.65	12.573%	$125.6878	$125.69	$125.70	$125.70
Purchase #7	$104.92	13.274%	$118.8471	$118.85	$118.85	$118.80
7 purchase totals =	$1,013.89		$1,101.0953	$1,101.10	$1,101.10	$1,101.10