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	$47.29	9.502%	$51.7835	$51.78	$51.80	$51.80
Purchase #2	$65.94	7.754%	$71.053	$71.05	$71.05	$71.10
Purchase #3	$124.82	7.306%	$133.9393	$133.94	$133.95	$133.90
Purchase #4	$202.50	9.619%	$221.9785	$221.98	$222.00	$222.00
Purchase #5	$208.89	12.769%	$235.5632	$235.56	$235.55	$235.60
Purchase #6	$172.59	10.162%	$190.1286	$190.13	$190.15	$190.10
Purchase #7	$110.78	5.722%	$117.1188	$117.12	$117.10	$117.10
7 purchase totals =	$932.81		$1,021.5649	$1,021.56	$1,021.60	$1,021.60