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	$112.90	4.125%	$117.5571	$117.56	$117.55	$117.60
Purchase #2	$201.51	4.656%	$210.8923	$210.89	$210.90	$210.90
Purchase #3	$90.26	11.426%	$100.5731	$100.57	$100.55	$100.60
Purchase #4	$123.30	13.799%	$140.3142	$140.31	$140.30	$140.30
Purchase #5	$50.34	4.147%	$52.4276	$52.43	$52.45	$52.40
Purchase #6	$126.51	13.308%	$143.346	$143.35	$143.35	$143.30
Purchase #7	$171.88	7.672%	$185.0666	$185.07	$185.05	$185.10
7 purchase totals =	$876.70		$950.1769	$950.18	$950.15	$950.20