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	$34.43	10.204%	$37.9432	$37.94	$37.95	$37.90
Purchase #2	$226.87	3.574%	$234.9783	$234.98	$235.00	$235.00
Purchase #3	$213.79	13.853%	$243.4063	$243.41	$243.40	$243.40
Purchase #4	$62.59	4.538%	$65.4303	$65.43	$65.45	$65.40
Purchase #5	$135.77	10.735%	$150.3449	$150.34	$150.35	$150.30
Purchase #6	$134.46	3.545%	$139.2266	$139.23	$139.25	$139.20
Purchase #7	$208.35	11.567%	$232.4498	$232.45	$232.45	$232.40
7 purchase totals =	$1,016.26		$1,103.7794	$1,103.78	$1,103.85	$1,103.60