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	$196.66	4.811%	$206.1213	$206.12	$206.10	$206.10
Purchase #2	$45.54	13.852%	$51.8482	$51.85	$51.85	$51.80
Purchase #3	$164.64	10.548%	$182.0062	$182.01	$182.00	$182.00
Purchase #4	$61.47	9.661%	$67.4086	$67.41	$67.40	$67.40
Purchase #5	$146.89	12.867%	$165.7903	$165.79	$165.80	$165.80
Purchase #6	$91.80	11.602%	$102.4506	$102.45	$102.45	$102.50
Purchase #7	$106.72	11.215%	$118.6886	$118.69	$118.70	$118.70
7 purchase totals =	$813.72		$894.3138	$894.32	$894.30	$894.30