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	$196.78	7.151%	$210.8517	$210.85	$210.85	$210.90
Purchase #2	$21.91	6.675%	$23.3725	$23.37	$23.35	$23.40
Purchase #3	$78.46	5.122%	$82.4787	$82.48	$82.50	$82.50
Purchase #4	$233.31	11.756%	$260.7379	$260.74	$260.75	$260.70
Purchase #5	$34.90	6.166%	$37.0519	$37.05	$37.05	$37.10
Purchase #6	$105.87	12.562%	$119.1694	$119.17	$119.15	$119.20
Purchase #7	$60.95	9.578%	$66.7878	$66.79	$66.80	$66.80
7 purchase totals =	$732.18		$800.4499	$800.45	$800.45	$800.60