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	$197.91	7.173%	$212.1061	$212.11	$212.10	$212.10
Purchase #2	$123.88	5.779%	$131.039	$131.04	$131.05	$131.00
Purchase #3	$179.57	10.764%	$198.8989	$198.90	$198.90	$198.90
Purchase #4	$73.50	7.266%	$78.8405	$78.84	$78.85	$78.80
Purchase #5	$153.92	11.268%	$171.2637	$171.26	$171.25	$171.30
Purchase #6	$192.42	12.466%	$216.4071	$216.41	$216.40	$216.40
Purchase #7	$151.70	13.115%	$171.5955	$171.60	$171.60	$171.60
7 purchase totals =	$1,072.90		$1,180.1508	$1,180.16	$1,180.15	$1,180.10