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	$12.62	11.552%	$14.0779	$14.08	$14.10	$14.10
Purchase #2	$88.53	13.116%	$100.1416	$100.14	$100.15	$100.10
Purchase #3	$223.30	11.168%	$248.2381	$248.24	$248.25	$248.20
Purchase #4	$55.74	3.361%	$57.6134	$57.61	$57.60	$57.60
Purchase #5	$60.93	6.309%	$64.7741	$64.77	$64.75	$64.80
Purchase #6	$52.83	12.314%	$59.3355	$59.34	$59.35	$59.30
Purchase #7	$121.99	7.119%	$130.6745	$130.67	$130.65	$130.70
7 purchase totals =	$615.94		$674.8551	$674.85	$674.85	$674.80