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	$147.77	4.351%	$154.1995	$154.20	$154.20	$154.20
Purchase #2	$26.92	5.272%	$28.3392	$28.34	$28.35	$28.30
Purchase #3	$191.63	12.868%	$216.2889	$216.29	$216.30	$216.30
Purchase #4	$218.30	7.308%	$234.2534	$234.25	$234.25	$234.30
Purchase #5	$132.54	13.204%	$150.0406	$150.04	$150.05	$150.00
Purchase #6	$182.41	7.689%	$196.4355	$196.44	$196.45	$196.40
Purchase #7	$51.67	3.470%	$53.4629	$53.46	$53.45	$53.50
7 purchase totals =	$951.24		$1,033.0200	$1,033.02	$1,033.05	$1,033.00