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	$89.80	7.168%	$96.2369	$96.24	$96.25	$96.20
Purchase #2	$212.63	3.719%	$220.5377	$220.54	$220.55	$220.50
Purchase #3	$75.73	7.654%	$81.5264	$81.53	$81.55	$81.50
Purchase #4	$63.77	12.549%	$71.7725	$71.77	$71.75	$71.80
Purchase #5	$17.53	5.593%	$18.5105	$18.51	$18.50	$18.50
Purchase #6	$35.43	5.565%	$37.4017	$37.40	$37.40	$37.40
Purchase #7	$83.30	10.332%	$91.9066	$91.91	$91.90	$91.90
7 purchase totals =	$578.19		$617.8923	$617.90	$617.90	$617.80