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	$225.90	8.206%	$244.4374	$244.44	$244.45	$244.40
Purchase #2	$132.58	3.830%	$137.6578	$137.66	$137.65	$137.70
Purchase #3	$135.46	4.282%	$141.2604	$141.26	$141.25	$141.30
Purchase #4	$94.30	11.822%	$105.4481	$105.45	$105.45	$105.40
Purchase #5	$75.45	6.274%	$80.1837	$80.18	$80.20	$80.20
Purchase #6	$145.46	3.325%	$150.2965	$150.30	$150.30	$150.30
Purchase #7	$211.57	13.516%	$240.1658	$240.17	$240.15	$240.20
7 purchase totals =	$1,020.72		$1,099.4497	$1,099.46	$1,099.45	$1,099.50