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	$239.50	6.428%	$254.8951	$254.90	$254.90	$254.90
Purchase #2	$177.91	7.292%	$190.8832	$190.88	$190.90	$190.90
Purchase #3	$87.49	3.655%	$90.6878	$90.69	$90.70	$90.70
Purchase #4	$241.33	9.686%	$264.7052	$264.71	$264.70	$264.70
Purchase #5	$148.89	5.539%	$157.137	$157.14	$157.15	$157.10
Purchase #6	$7.97	5.444%	$8.4039	$8.40	$8.40	$8.40
Purchase #7	$79.71	12.767%	$89.8866	$89.89	$89.90	$89.90
7 purchase totals =	$982.80		$1,056.5988	$1,056.61	$1,056.65	$1,056.60