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	$172.52	9.500%	$188.9094	$188.91	$188.90	$188.90
Purchase #2	$250.41	9.211%	$273.4753	$273.48	$273.50	$273.50
Purchase #3	$13.42	10.738%	$14.861	$14.86	$14.85	$14.90
Purchase #4	$166.80	3.389%	$172.4529	$172.45	$172.45	$172.50
Purchase #5	$135.80	4.242%	$141.5606	$141.56	$141.55	$141.60
Purchase #6	$115.57	9.378%	$126.4082	$126.41	$126.40	$126.40
Purchase #7	$97.84	6.682%	$104.3777	$104.38	$104.40	$104.40
7 purchase totals =	$952.36		$1,022.0451	$1,022.05	$1,022.05	$1,022.20