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	$246.56	7.682%	$265.5007	$265.50	$265.50	$265.50
Purchase #2	$70.64	7.732%	$76.1019	$76.10	$76.10	$76.10
Purchase #3	$180.57	5.519%	$190.5357	$190.54	$190.55	$190.50
Purchase #4	$201.90	11.158%	$224.428	$224.43	$224.45	$224.40
Purchase #5	$83.29	7.443%	$89.4893	$89.49	$89.50	$89.50
Purchase #6	$110.47	7.682%	$118.9563	$118.96	$118.95	$119.00
Purchase #7	$25.77	11.388%	$28.7047	$28.70	$28.70	$28.70
7 purchase totals =	$919.20		$993.7166	$993.72	$993.75	$993.70