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	$99.94	12.840%	$112.7723	$112.77	$112.75	$112.80
Purchase #2	$9.93	9.575%	$10.8808	$10.88	$10.90	$10.90
Purchase #3	$49.37	9.630%	$54.1243	$54.12	$54.10	$54.10
Purchase #4	$87.63	11.833%	$97.9993	$98.00	$98.00	$98.00
Purchase #5	$105.89	6.333%	$112.596	$112.60	$112.60	$112.60
Purchase #6	$82.44	10.514%	$91.1077	$91.11	$91.10	$91.10
Purchase #7	$103.99	7.754%	$112.0534	$112.05	$112.05	$112.10
7 purchase totals =	$539.19		$591.5338	$591.53	$591.50	$591.60