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	$132.82	5.193%	$139.7173	$139.72	$139.70	$139.70
Purchase #2	$68.47	5.528%	$72.255	$72.26	$72.25	$72.30
Purchase #3	$8.46	12.465%	$9.5145	$9.51	$9.50	$9.50
Purchase #4	$53.39	12.543%	$60.0867	$60.09	$60.10	$60.10
Purchase #5	$249.59	4.389%	$260.5445	$260.54	$260.55	$260.50
Purchase #6	$83.37	7.372%	$89.516	$89.52	$89.50	$89.50
Purchase #7	$221.86	10.489%	$245.1309	$245.13	$245.15	$245.10
7 purchase totals =	$817.96		$876.7649	$876.77	$876.75	$876.70