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	$199.62	5.134%	$209.8685	$209.87	$209.85	$209.90
Purchase #2	$234.83	3.226%	$242.4056	$242.41	$242.40	$242.40
Purchase #3	$175.95	11.640%	$196.4306	$196.43	$196.45	$196.40
Purchase #4	$50.45	3.164%	$52.0462	$52.05	$52.05	$52.00
Purchase #5	$52.70	7.266%	$56.5292	$56.53	$56.55	$56.50
Purchase #6	$139.53	3.438%	$144.327	$144.33	$144.35	$144.30
Purchase #7	$245.26	13.741%	$278.9612	$278.96	$278.95	$279.00
7 purchase totals =	$1,098.34		$1,180.5683	$1,180.58	$1,180.60	$1,180.50