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	$215.89	12.780%	$243.4807	$243.48	$243.50	$243.50
Purchase #2	$160.32	3.516%	$165.9569	$165.96	$165.95	$166.00
Purchase #3	$57.29	3.778%	$59.4544	$59.45	$59.45	$59.50
Purchase #4	$241.81	4.356%	$252.3432	$252.34	$252.35	$252.30
Purchase #5	$231.68	11.565%	$258.4738	$258.47	$258.45	$258.50
Purchase #6	$96.58	12.811%	$108.9529	$108.95	$108.95	$109.00
Purchase #7	$7.29	5.245%	$7.6724	$7.67	$7.65	$7.70
7 purchase totals =	$1,010.86		$1,096.3343	$1,096.32	$1,096.30	$1,096.50