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	$40.79	7.786%	$43.9659	$43.97	$43.95	$44.00
Purchase #2	$216.60	10.715%	$239.8087	$239.81	$239.80	$239.80
Purchase #3	$33.71	13.846%	$38.3775	$38.38	$38.40	$38.40
Purchase #4	$219.30	11.394%	$244.287	$244.29	$244.30	$244.30
Purchase #5	$34.76	6.850%	$37.1411	$37.14	$37.15	$37.10
Purchase #6	$78.46	8.707%	$85.2915	$85.29	$85.30	$85.30
Purchase #7	$36.43	3.119%	$37.5663	$37.57	$37.55	$37.60
7 purchase totals =	$660.05		$726.4380	$726.45	$726.45	$726.50