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	$89.94	4.680%	$94.1492	$94.15	$94.15	$94.10
Purchase #2	$84.31	7.159%	$90.3458	$90.35	$90.35	$90.30
Purchase #3	$108.79	11.785%	$121.6109	$121.61	$121.60	$121.60
Purchase #4	$149.90	13.551%	$170.2129	$170.21	$170.20	$170.20
Purchase #5	$88.38	4.427%	$92.2926	$92.29	$92.30	$92.30
Purchase #6	$86.95	3.123%	$89.6654	$89.67	$89.65	$89.70
Purchase #7	$95.89	6.704%	$102.3185	$102.32	$102.30	$102.30
7 purchase totals =	$704.16		$760.5953	$760.60	$760.55	$760.50