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	$200.34	11.525%	$223.4292	$223.43	$223.45	$223.40
Purchase #2	$194.50	12.153%	$218.1376	$218.14	$218.15	$218.10
Purchase #3	$53.89	6.844%	$57.5782	$57.58	$57.60	$57.60
Purchase #4	$136.80	3.645%	$141.7864	$141.79	$141.80	$141.80
Purchase #5	$33.96	9.627%	$37.2293	$37.23	$37.25	$37.20
Purchase #6	$64.50	3.427%	$66.7104	$66.71	$66.70	$66.70
Purchase #7	$77.70	7.199%	$83.2936	$83.29	$83.30	$83.30
7 purchase totals =	$761.69		$828.1647	$828.17	$828.25	$828.10