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	$192.36	4.404%	$200.8315	$200.83	$200.85	$200.80
Purchase #2	$97.74	12.341%	$109.8021	$109.80	$109.80	$109.80
Purchase #3	$70.33	8.278%	$76.1519	$76.15	$76.15	$76.20
Purchase #4	$45.48	4.355%	$47.4607	$47.46	$47.45	$47.50
Purchase #5	$204.31	10.550%	$225.8647	$225.86	$225.85	$225.90
Purchase #6	$196.88	6.104%	$208.8976	$208.90	$208.90	$208.90
Purchase #7	$207.31	8.105%	$224.1125	$224.11	$224.10	$224.10
7 purchase totals =	$1,014.41		$1,093.1210	$1,093.11	$1,093.10	$1,093.20