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	$192.80	8.123%	$208.4611	$208.46	$208.45	$208.50
Purchase #2	$131.40	4.648%	$137.5075	$137.51	$137.50	$137.50
Purchase #3	$152.33	4.794%	$159.6327	$159.63	$159.65	$159.60
Purchase #4	$130.82	9.475%	$143.2152	$143.22	$143.20	$143.20
Purchase #5	$91.41	11.476%	$101.9002	$101.90	$101.90	$101.90
Purchase #6	$223.65	6.484%	$238.1515	$238.15	$238.15	$238.20
Purchase #7	$13.60	9.749%	$14.9259	$14.93	$14.95	$14.90
7 purchase totals =	$936.01		$1,003.7941	$1,003.80	$1,003.80	$1,003.80