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	$110.66	7.846%	$119.3424	$119.34	$119.35	$119.30
Purchase #2	$123.88	7.124%	$132.7052	$132.71	$132.70	$132.70
Purchase #3	$88.78	11.668%	$99.1389	$99.14	$99.15	$99.10
Purchase #4	$90.76	9.238%	$99.1444	$99.14	$99.15	$99.10
Purchase #5	$97.93	13.377%	$111.0301	$111.03	$111.05	$111.00
Purchase #6	$222.98	11.525%	$248.6784	$248.68	$248.70	$248.70
Purchase #7	$217.55	9.308%	$237.7996	$237.80	$237.80	$237.80
7 purchase totals =	$952.54		$1,047.8390	$1,047.84	$1,047.90	$1,047.70