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	$140.62	5.794%	$148.7675	$148.77	$148.75	$148.80
Purchase #2	$225.34	5.787%	$238.3804	$238.38	$238.40	$238.40
Purchase #3	$241.32	13.284%	$273.3769	$273.38	$273.40	$273.40
Purchase #4	$123.36	3.243%	$127.3606	$127.36	$127.35	$127.40
Purchase #5	$129.36	3.494%	$133.8798	$133.88	$133.90	$133.90
Purchase #6	$71.47	6.451%	$76.0805	$76.08	$76.10	$76.10
Purchase #7	$245.37	4.151%	$255.5553	$255.56	$255.55	$255.60
7 purchase totals =	$1,176.84		$1,253.4010	$1,253.41	$1,253.45	$1,253.60