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	$108.78	3.302%	$112.3719	$112.37	$112.35	$112.40
Purchase #2	$97.30	3.413%	$100.6208	$100.62	$100.60	$100.60
Purchase #3	$165.78	4.206%	$172.7527	$172.75	$172.75	$172.80
Purchase #4	$167.90	13.156%	$189.9889	$189.99	$190.00	$190.00
Purchase #5	$39.53	12.667%	$44.5373	$44.54	$44.55	$44.50
Purchase #6	$165.74	10.291%	$182.7963	$182.80	$182.80	$182.80
Purchase #7	$152.46	12.484%	$171.4931	$171.49	$171.50	$171.50
7 purchase totals =	$897.49		$974.5610	$974.56	$974.55	$974.60