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	$169.54	7.282%	$181.8859	$181.89	$181.90	$181.90
Purchase #2	$139.39	13.131%	$157.6933	$157.69	$157.70	$157.70
Purchase #3	$195.51	12.586%	$220.1169	$220.12	$220.10	$220.10
Purchase #4	$198.92	11.716%	$222.2255	$222.23	$222.25	$222.20
Purchase #5	$20.96	7.169%	$22.4626	$22.46	$22.45	$22.50
Purchase #6	$215.50	3.677%	$223.4239	$223.42	$223.40	$223.40
Purchase #7	$81.55	10.128%	$89.8094	$89.81	$89.80	$89.80
7 purchase totals =	$1,021.37		$1,117.6175	$1,117.62	$1,117.60	$1,117.60