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	$39.73	3.361%	$41.0653	$41.07	$41.05	$41.10
Purchase #2	$95.88	5.133%	$100.8015	$100.80	$100.80	$100.80
Purchase #3	$41.51	9.126%	$45.2982	$45.30	$45.30	$45.30
Purchase #4	$34.53	3.128%	$35.6101	$35.61	$35.60	$35.60
Purchase #5	$95.69	8.606%	$103.9251	$103.93	$103.95	$103.90
Purchase #6	$129.63	11.765%	$144.881	$144.88	$144.90	$144.90
Purchase #7	$117.69	10.152%	$129.6379	$129.64	$129.65	$129.60
7 purchase totals =	$554.66		$601.2191	$601.23	$601.25	$601.20