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	$151.78	13.644%	$172.4889	$172.49	$172.50	$172.50
Purchase #2	$94.75	9.596%	$103.8422	$103.84	$103.85	$103.80
Purchase #3	$52.57	4.345%	$54.8542	$54.85	$54.85	$54.90
Purchase #4	$199.54	4.326%	$208.1721	$208.17	$208.15	$208.20
Purchase #5	$204.48	5.811%	$216.3623	$216.36	$216.35	$216.40
Purchase #6	$218.74	10.753%	$242.2611	$242.26	$242.25	$242.30
Purchase #7	$81.79	13.240%	$92.619	$92.62	$92.60	$92.60
7 purchase totals =	$1,003.65		$1,090.5998	$1,090.59	$1,090.55	$1,090.70