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	$155.83	4.545%	$162.9125	$162.91	$162.90	$162.90
Purchase #2	$12.66	5.162%	$13.3135	$13.31	$13.30	$13.30
Purchase #3	$221.79	6.526%	$236.264	$236.26	$236.25	$236.30
Purchase #4	$77.44	7.763%	$83.4517	$83.45	$83.45	$83.50
Purchase #5	$36.49	8.266%	$39.5063	$39.51	$39.50	$39.50
Purchase #6	$67.55	13.283%	$76.5227	$76.52	$76.50	$76.50
Purchase #7	$177.36	4.569%	$185.4636	$185.46	$185.45	$185.50
7 purchase totals =	$749.12		$797.4343	$797.42	$797.35	$797.50