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	$195.74	8.627%	$212.6265	$212.63	$212.65	$212.60
Purchase #2	$145.33	5.635%	$153.5193	$153.52	$153.50	$153.50
Purchase #3	$95.67	9.808%	$105.0533	$105.05	$105.05	$105.10
Purchase #4	$231.71	11.531%	$258.4285	$258.43	$258.45	$258.40
Purchase #5	$180.89	8.658%	$196.5515	$196.55	$196.55	$196.60
Purchase #6	$198.72	4.130%	$206.9271	$206.93	$206.95	$206.90
Purchase #7	$96.44	11.347%	$107.383	$107.38	$107.40	$107.40
7 purchase totals =	$1,144.50		$1,240.4892	$1,240.49	$1,240.55	$1,240.50