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	$46.59	12.589%	$52.4552	$52.46	$52.45	$52.50
Purchase #2	$61.76	9.864%	$67.852	$67.85	$67.85	$67.90
Purchase #3	$189.33	5.524%	$199.7886	$199.79	$199.80	$199.80
Purchase #4	$196.85	9.503%	$215.5567	$215.56	$215.55	$215.60
Purchase #5	$241.44	4.162%	$251.4887	$251.49	$251.50	$251.50
Purchase #6	$25.32	4.483%	$26.4551	$26.46	$26.45	$26.50
Purchase #7	$121.35	10.335%	$133.8915	$133.89	$133.90	$133.90
7 purchase totals =	$882.64		$947.4878	$947.50	$947.50	$947.70