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	$170.96	11.351%	$190.3657	$190.37	$190.35	$190.40
Purchase #2	$171.94	7.141%	$184.2182	$184.22	$184.20	$184.20
Purchase #3	$170.48	4.700%	$178.4926	$178.49	$178.50	$178.50
Purchase #4	$165.84	9.511%	$181.613	$181.61	$181.60	$181.60
Purchase #5	$59.46	5.873%	$62.9521	$62.95	$62.95	$63.00
Purchase #6	$170.54	8.805%	$185.556	$185.56	$185.55	$185.60
Purchase #7	$169.37	13.724%	$192.6143	$192.61	$192.60	$192.60
7 purchase totals =	$1,078.59		$1,175.8119	$1,175.81	$1,175.75	$1,175.90