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	$163.68	12.643%	$184.3741	$184.37	$184.35	$184.40
Purchase #2	$37.34	13.782%	$42.4862	$42.49	$42.50	$42.50
Purchase #3	$30.39	5.275%	$31.9931	$31.99	$32.00	$32.00
Purchase #4	$39.77	10.409%	$43.9097	$43.91	$43.90	$43.90
Purchase #5	$84.98	11.168%	$94.4706	$94.47	$94.45	$94.50
Purchase #6	$196.72	12.807%	$221.9139	$221.91	$221.90	$221.90
Purchase #7	$70.54	13.222%	$79.8668	$79.87	$79.85	$79.90
7 purchase totals =	$623.42		$699.0144	$699.01	$698.95	$699.10