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	$20.96	5.274%	$22.0654	$22.07	$22.05	$22.10
Purchase #2	$167.29	5.518%	$176.5211	$176.52	$176.50	$176.50
Purchase #3	$243.46	12.377%	$273.593	$273.59	$273.60	$273.60
Purchase #4	$147.50	3.429%	$152.5578	$152.56	$152.55	$152.60
Purchase #5	$50.89	13.695%	$57.8594	$57.86	$57.85	$57.90
Purchase #6	$200.88	13.756%	$228.5131	$228.51	$228.50	$228.50
Purchase #7	$227.30	10.559%	$251.3006	$251.30	$251.30	$251.30
7 purchase totals =	$1,058.28		$1,162.4104	$1,162.41	$1,162.35	$1,162.50