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	$38.41	11.786%	$42.937	$42.94	$42.95	$42.90
Purchase #2	$124.62	10.390%	$137.568	$137.57	$137.55	$137.60
Purchase #3	$62.92	13.360%	$71.3261	$71.33	$71.35	$71.30
Purchase #4	$88.90	8.303%	$96.2814	$96.28	$96.30	$96.30
Purchase #5	$147.60	4.111%	$153.6678	$153.67	$153.65	$153.70
Purchase #6	$205.83	8.292%	$222.8974	$222.90	$222.90	$222.90
Purchase #7	$169.56	8.224%	$183.5046	$183.50	$183.50	$183.50
7 purchase totals =	$837.84		$908.1823	$908.19	$908.20	$908.20