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	$164.66	12.760%	$185.6706	$185.67	$185.65	$185.70
Purchase #2	$29.74	12.685%	$33.5125	$33.51	$33.50	$33.50
Purchase #3	$45.36	8.180%	$49.0704	$49.07	$49.05	$49.10
Purchase #4	$114.93	11.294%	$127.9102	$127.91	$127.90	$127.90
Purchase #5	$133.46	3.639%	$138.3166	$138.32	$138.30	$138.30
Purchase #6	$136.40	5.650%	$144.1066	$144.11	$144.10	$144.10
Purchase #7	$246.93	10.757%	$273.4923	$273.49	$273.50	$273.50
7 purchase totals =	$871.48		$952.0792	$952.08	$952.00	$952.10