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	$243.40	6.829%	$260.0218	$260.02	$260.00	$260.00
Purchase #2	$145.64	13.668%	$165.5461	$165.55	$165.55	$165.50
Purchase #3	$49.33	5.858%	$52.2198	$52.22	$52.20	$52.20
Purchase #4	$45.40	7.568%	$48.8359	$48.84	$48.85	$48.80
Purchase #5	$140.49	4.204%	$146.3962	$146.40	$146.40	$146.40
Purchase #6	$125.79	4.763%	$131.7814	$131.78	$131.80	$131.80
Purchase #7	$246.47	4.611%	$257.8347	$257.83	$257.85	$257.80
7 purchase totals =	$996.52		$1,062.6359	$1,062.64	$1,062.65	$1,062.50