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	$63.89	11.541%	$71.2635	$71.26	$71.25	$71.30
Purchase #2	$234.26	5.494%	$247.1302	$247.13	$247.15	$247.10
Purchase #3	$80.54	7.815%	$86.8342	$86.83	$86.85	$86.80
Purchase #4	$222.46	13.352%	$252.1629	$252.16	$252.15	$252.20
Purchase #5	$82.30	3.464%	$85.1509	$85.15	$85.15	$85.20
Purchase #6	$155.94	8.590%	$169.3352	$169.34	$169.35	$169.30
Purchase #7	$178.25	12.526%	$200.5776	$200.58	$200.60	$200.60
7 purchase totals =	$1,017.64		$1,112.4545	$1,112.45	$1,112.50	$1,112.50