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	$145.40	3.549%	$150.5602	$150.56	$150.55	$150.60
Purchase #2	$166.28	3.754%	$172.5222	$172.52	$172.50	$172.50
Purchase #3	$169.77	12.406%	$190.8317	$190.83	$190.85	$190.80
Purchase #4	$161.84	11.565%	$180.5568	$180.56	$180.55	$180.60
Purchase #5	$109.57	9.708%	$120.2071	$120.21	$120.20	$120.20
Purchase #6	$222.57	3.667%	$230.7316	$230.73	$230.75	$230.70
Purchase #7	$204.59	9.757%	$224.5518	$224.55	$224.55	$224.60
7 purchase totals =	$1,180.02		$1,269.9614	$1,269.96	$1,269.95	$1,270.00