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	$13.28	9.464%	$14.5368	$14.54	$14.55	$14.50
Purchase #2	$78.30	10.333%	$86.3907	$86.39	$86.40	$86.40
Purchase #3	$133.54	8.485%	$144.8709	$144.87	$144.85	$144.90
Purchase #4	$126.41	10.673%	$139.9017	$139.90	$139.90	$139.90
Purchase #5	$17.46	7.705%	$18.8053	$18.81	$18.80	$18.80
Purchase #6	$91.44	8.415%	$99.1347	$99.13	$99.15	$99.10
Purchase #7	$10.49	7.797%	$11.3079	$11.31	$11.30	$11.30
7 purchase totals =	$470.92		$514.9480	$514.95	$514.95	$514.90