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	$167.72	10.862%	$185.9377	$185.94	$185.95	$185.90
Purchase #2	$86.64	5.218%	$91.1609	$91.16	$91.15	$91.20
Purchase #3	$156.92	4.438%	$163.8841	$163.88	$163.90	$163.90
Purchase #4	$42.88	13.282%	$48.5753	$48.58	$48.60	$48.60
Purchase #5	$244.29	10.290%	$269.4274	$269.43	$269.45	$269.40
Purchase #6	$245.61	3.388%	$253.9313	$253.93	$253.95	$253.90
Purchase #7	$40.60	10.558%	$44.8865	$44.89	$44.90	$44.90
7 purchase totals =	$984.66		$1,057.8032	$1,057.81	$1,057.90	$1,057.80