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	$142.64	5.180%	$150.0288	$150.03	$150.05	$150.00
Purchase #2	$45.51	5.710%	$48.1086	$48.11	$48.10	$48.10
Purchase #3	$13.60	3.185%	$14.0332	$14.03	$14.05	$14.00
Purchase #4	$71.58	9.473%	$78.3608	$78.36	$78.35	$78.40
Purchase #5	$33.46	13.328%	$37.9195	$37.92	$37.90	$37.90
Purchase #6	$240.73	13.336%	$272.8338	$272.83	$272.85	$272.80
Purchase #7	$155.29	10.344%	$171.3532	$171.35	$171.35	$171.40
7 purchase totals =	$702.81		$772.6379	$772.63	$772.65	$772.60