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	$99.34	5.648%	$104.9507	$104.95	$104.95	$105.00
Purchase #2	$119.49	6.132%	$126.8171	$126.82	$126.80	$126.80
Purchase #3	$80.85	11.478%	$90.13	$90.13	$90.15	$90.10
Purchase #4	$111.78	5.579%	$118.0162	$118.02	$118.00	$118.00
Purchase #5	$56.56	10.307%	$62.3896	$62.39	$62.40	$62.40
Purchase #6	$154.27	9.858%	$169.4779	$169.48	$169.50	$169.50
Purchase #7	$26.90	10.342%	$29.682	$29.68	$29.70	$29.70
7 purchase totals =	$649.19		$701.4635	$701.47	$701.50	$701.50