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	$211.51	6.663%	$225.6029	$225.60	$225.60	$225.60
Purchase #2	$186.71	10.272%	$205.8889	$205.89	$205.90	$205.90
Purchase #3	$206.85	3.250%	$213.5726	$213.57	$213.55	$213.60
Purchase #4	$40.53	12.518%	$45.6035	$45.60	$45.60	$45.60
Purchase #5	$67.47	8.571%	$73.2529	$73.25	$73.25	$73.30
Purchase #6	$154.95	11.490%	$172.7538	$172.75	$172.75	$172.80
Purchase #7	$89.96	3.866%	$93.4379	$93.44	$93.45	$93.40
7 purchase totals =	$957.98		$1,030.1125	$1,030.10	$1,030.10	$1,030.20