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	$19.45	13.153%	$22.0083	$22.01	$22.00	$22.00
Purchase #2	$71.87	9.705%	$78.845	$78.85	$78.85	$78.80
Purchase #3	$223.39	12.699%	$251.7583	$251.76	$251.75	$251.80
Purchase #4	$65.57	9.528%	$71.8175	$71.82	$71.80	$71.80
Purchase #5	$164.38	9.718%	$180.3544	$180.35	$180.35	$180.40
Purchase #6	$213.49	4.620%	$223.3532	$223.35	$223.35	$223.40
Purchase #7	$187.63	4.359%	$195.8088	$195.81	$195.80	$195.80
7 purchase totals =	$945.78		$1,023.9455	$1,023.95	$1,023.90	$1,024.00