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	$87.93	10.374%	$97.0519	$97.05	$97.05	$97.10
Purchase #2	$38.46	10.516%	$42.5045	$42.50	$42.50	$42.50
Purchase #3	$217.72	3.128%	$224.5303	$224.53	$224.55	$224.50
Purchase #4	$35.94	3.542%	$37.213	$37.21	$37.20	$37.20
Purchase #5	$27.39	10.635%	$30.3029	$30.30	$30.30	$30.30
Purchase #6	$208.81	4.629%	$218.4758	$218.48	$218.50	$218.50
Purchase #7	$98.43	13.598%	$111.8145	$111.81	$111.80	$111.80
7 purchase totals =	$714.68		$761.8929	$761.88	$761.90	$761.90