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	$149.62	8.574%	$162.4484	$162.45	$162.45	$162.40
Purchase #2	$74.78	3.741%	$77.5775	$77.58	$77.60	$77.60
Purchase #3	$146.28	7.676%	$157.5085	$157.51	$157.50	$157.50
Purchase #4	$140.69	12.740%	$158.6139	$158.61	$158.60	$158.60
Purchase #5	$123.81	12.721%	$139.5599	$139.56	$139.55	$139.60
Purchase #6	$92.64	10.779%	$102.6257	$102.63	$102.65	$102.60
Purchase #7	$126.78	11.831%	$141.7793	$141.78	$141.80	$141.80
7 purchase totals =	$854.60		$940.1132	$940.12	$940.15	$940.10