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	$74.94	10.853%	$83.0732	$83.07	$83.05	$83.10
Purchase #2	$223.35	3.506%	$231.1807	$231.18	$231.20	$231.20
Purchase #3	$204.46	8.445%	$221.7266	$221.73	$221.75	$221.70
Purchase #4	$206.53	8.705%	$224.5084	$224.51	$224.50	$224.50
Purchase #5	$50.48	6.762%	$53.8935	$53.89	$53.90	$53.90
Purchase #6	$192.27	12.801%	$216.8825	$216.88	$216.90	$216.90
Purchase #7	$63.80	6.133%	$67.7129	$67.71	$67.70	$67.70
7 purchase totals =	$1,015.83		$1,098.9778	$1,098.97	$1,099.00	$1,099.00