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	$197.49	3.557%	$204.5147	$204.51	$204.50	$204.50
Purchase #2	$71.32	9.659%	$78.2088	$78.21	$78.20	$78.20
Purchase #3	$150.78	13.205%	$170.6905	$170.69	$170.70	$170.70
Purchase #4	$77.92	6.816%	$83.231	$83.23	$83.25	$83.20
Purchase #5	$200.75	11.834%	$224.5068	$224.51	$224.50	$224.50
Purchase #6	$143.90	11.210%	$160.0312	$160.03	$160.05	$160.00
Purchase #7	$85.61	6.700%	$91.3459	$91.35	$91.35	$91.30
7 purchase totals =	$927.77		$1,012.5289	$1,012.53	$1,012.55	$1,012.40