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	$68.68	4.743%	$71.9375	$71.94	$71.95	$71.90
Purchase #2	$32.89	13.653%	$37.3805	$37.38	$37.40	$37.40
Purchase #3	$242.31	8.768%	$263.5557	$263.56	$263.55	$263.60
Purchase #4	$32.49	4.850%	$34.0658	$34.07	$34.05	$34.10
Purchase #5	$236.78	3.480%	$245.0199	$245.02	$245.00	$245.00
Purchase #6	$111.47	3.321%	$115.1719	$115.17	$115.15	$115.20
Purchase #7	$50.46	10.612%	$55.8148	$55.81	$55.80	$55.80
7 purchase totals =	$775.08		$822.9461	$822.95	$822.90	$823.00