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	$62.39	8.362%	$67.6071	$67.61	$67.60	$67.60
Purchase #2	$23.42	10.638%	$25.9114	$25.91	$25.90	$25.90
Purchase #3	$148.94	7.273%	$159.7724	$159.77	$159.75	$159.80
Purchase #4	$243.34	12.818%	$274.5313	$274.53	$274.55	$274.50
Purchase #5	$171.94	10.525%	$190.0367	$190.04	$190.05	$190.00
Purchase #6	$69.82	5.335%	$73.5449	$73.54	$73.55	$73.50
Purchase #7	$152.72	3.114%	$157.4757	$157.48	$157.50	$157.50
7 purchase totals =	$872.57		$948.8795	$948.88	$948.90	$948.80