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	$55.66	10.212%	$61.344	$61.34	$61.35	$61.30
Purchase #2	$90.78	12.462%	$102.093	$102.09	$102.10	$102.10
Purchase #3	$142.49	5.470%	$150.2842	$150.28	$150.30	$150.30
Purchase #4	$206.82	13.372%	$234.476	$234.48	$234.50	$234.50
Purchase #5	$232.95	11.516%	$259.7765	$259.78	$259.80	$259.80
Purchase #6	$30.31	6.387%	$32.2459	$32.25	$32.25	$32.20
Purchase #7	$197.73	6.163%	$209.9161	$209.92	$209.90	$209.90
7 purchase totals =	$956.74		$1,050.1357	$1,050.14	$1,050.20	$1,050.10