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	$218.38	12.578%	$245.8478	$245.85	$245.85	$245.80
Purchase #2	$33.52	13.276%	$37.9701	$37.97	$37.95	$38.00
Purchase #3	$93.70	5.650%	$98.9941	$98.99	$99.00	$99.00
Purchase #4	$125.27	5.283%	$131.888	$131.89	$131.90	$131.90
Purchase #5	$15.88	3.196%	$16.3875	$16.39	$16.40	$16.40
Purchase #6	$148.79	8.132%	$160.8896	$160.89	$160.90	$160.90
Purchase #7	$147.61	4.695%	$154.5403	$154.54	$154.55	$154.50
7 purchase totals =	$783.15		$846.5174	$846.52	$846.55	$846.50