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	$66.79	8.475%	$72.4505	$72.45	$72.45	$72.50
Purchase #2	$143.53	8.600%	$155.8736	$155.87	$155.85	$155.90
Purchase #3	$188.84	9.110%	$206.0433	$206.04	$206.05	$206.00
Purchase #4	$243.36	6.807%	$259.9255	$259.93	$259.95	$259.90
Purchase #5	$74.45	10.833%	$82.5152	$82.52	$82.50	$82.50
Purchase #6	$182.76	12.794%	$206.1423	$206.14	$206.15	$206.10
Purchase #7	$149.49	12.870%	$168.7294	$168.73	$168.75	$168.70
7 purchase totals =	$1,049.22		$1,151.6798	$1,151.68	$1,151.70	$1,151.60