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	$142.39	9.608%	$156.0708	$156.07	$156.05	$156.10
Purchase #2	$7.61	3.511%	$7.8772	$7.88	$7.90	$7.90
Purchase #3	$86.36	9.252%	$94.35	$94.35	$94.35	$94.40
Purchase #4	$38.50	12.266%	$43.2224	$43.22	$43.20	$43.20
Purchase #5	$135.94	12.412%	$152.8129	$152.81	$152.80	$152.80
Purchase #6	$122.52	12.124%	$137.3743	$137.37	$137.35	$137.40
Purchase #7	$61.28	5.761%	$64.8103	$64.81	$64.80	$64.80
7 purchase totals =	$594.60		$656.5179	$656.51	$656.45	$656.60