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	$54.78	8.630%	$59.5075	$59.51	$59.50	$59.50
Purchase #2	$220.73	13.761%	$251.1047	$251.10	$251.10	$251.10
Purchase #3	$42.80	5.323%	$45.0782	$45.08	$45.10	$45.10
Purchase #4	$180.66	6.645%	$192.6649	$192.66	$192.65	$192.70
Purchase #5	$248.51	6.112%	$263.6989	$263.70	$263.70	$263.70
Purchase #6	$114.94	3.120%	$118.5261	$118.53	$118.55	$118.50
Purchase #7	$90.33	11.312%	$100.5481	$100.55	$100.55	$100.50
7 purchase totals =	$952.75		$1,031.1284	$1,031.13	$1,031.15	$1,031.10