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	$58.84	13.621%	$66.8546	$66.85	$66.85	$66.90
Purchase #2	$124.73	5.121%	$131.1174	$131.12	$131.10	$131.10
Purchase #3	$65.66	11.829%	$73.4269	$73.43	$73.45	$73.40
Purchase #4	$95.82	4.419%	$100.0543	$100.05	$100.05	$100.10
Purchase #5	$234.78	11.521%	$261.829	$261.83	$261.85	$261.80
Purchase #6	$247.46	10.685%	$273.9011	$273.90	$273.90	$273.90
Purchase #7	$214.73	3.386%	$222.0008	$222.00	$222.00	$222.00
7 purchase totals =	$1,042.02		$1,129.1841	$1,129.18	$1,129.20	$1,129.20