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	$172.91	13.256%	$195.8309	$195.83	$195.85	$195.80
Purchase #2	$180.70	11.134%	$200.8191	$200.82	$200.80	$200.80
Purchase #3	$6.81	8.683%	$7.4013	$7.40	$7.40	$7.40
Purchase #4	$64.46	11.671%	$71.9831	$71.98	$72.00	$72.00
Purchase #5	$233.56	13.659%	$265.462	$265.46	$265.45	$265.50
Purchase #6	$115.56	12.510%	$130.0166	$130.02	$130.00	$130.00
Purchase #7	$45.80	3.645%	$47.4694	$47.47	$47.45	$47.50
7 purchase totals =	$819.80		$918.9824	$918.98	$918.95	$919.00