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	$19.59	13.767%	$22.287	$22.29	$22.30	$22.30
Purchase #2	$245.55	11.725%	$274.3407	$274.34	$274.35	$274.30
Purchase #3	$47.76	4.569%	$49.9422	$49.94	$49.95	$49.90
Purchase #4	$40.78	13.483%	$46.2784	$46.28	$46.30	$46.30
Purchase #5	$141.76	6.442%	$150.8922	$150.89	$150.90	$150.90
Purchase #6	$225.34	7.859%	$243.0495	$243.05	$243.05	$243.00
Purchase #7	$218.94	7.606%	$235.5926	$235.59	$235.60	$235.60
7 purchase totals =	$939.72		$1,022.3826	$1,022.38	$1,022.45	$1,022.30