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	$108.67	8.458%	$117.8613	$117.86	$117.85	$117.90
Purchase #2	$51.34	13.427%	$58.2334	$58.23	$58.25	$58.20
Purchase #3	$127.54	10.385%	$140.785	$140.79	$140.80	$140.80
Purchase #4	$181.46	4.802%	$190.1737	$190.17	$190.15	$190.20
Purchase #5	$63.34	3.346%	$65.4594	$65.46	$65.45	$65.50
Purchase #6	$74.78	3.725%	$77.5656	$77.57	$77.55	$77.60
Purchase #7	$175.85	11.717%	$196.4543	$196.45	$196.45	$196.50
7 purchase totals =	$782.98		$846.5327	$846.53	$846.50	$846.70