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	$106.60	10.612%	$117.9124	$117.91	$117.90	$117.90
Purchase #2	$35.58	4.105%	$37.0406	$37.04	$37.05	$37.00
Purchase #3	$88.90	4.220%	$92.6516	$92.65	$92.65	$92.70
Purchase #4	$24.33	4.357%	$25.3901	$25.39	$25.40	$25.40
Purchase #5	$6.97	3.748%	$7.2312	$7.23	$7.25	$7.20
Purchase #6	$71.52	9.428%	$78.2629	$78.26	$78.25	$78.30
Purchase #7	$46.56	4.430%	$48.6226	$48.62	$48.60	$48.60
7 purchase totals =	$380.46		$407.1114	$407.10	$407.10	$407.10