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	$150.90	3.633%	$156.3822	$156.38	$156.40	$156.40
Purchase #2	$99.77	5.595%	$105.3521	$105.35	$105.35	$105.40
Purchase #3	$69.38	3.610%	$71.8846	$71.88	$71.90	$71.90
Purchase #4	$101.40	11.439%	$112.9991	$113.00	$113.00	$113.00
Purchase #5	$235.34	12.316%	$264.3245	$264.32	$264.30	$264.30
Purchase #6	$239.97	8.572%	$260.5402	$260.54	$260.55	$260.50
Purchase #7	$47.85	7.635%	$51.5033	$51.50	$51.50	$51.50
7 purchase totals =	$944.61		$1,022.9860	$1,022.97	$1,023.00	$1,023.00