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	$21.37	3.118%	$22.0363	$22.04	$22.05	$22.00
Purchase #2	$198.31	4.629%	$207.4898	$207.49	$207.50	$207.50
Purchase #3	$127.48	12.625%	$143.5744	$143.57	$143.55	$143.60
Purchase #4	$73.74	6.660%	$78.6511	$78.65	$78.65	$78.70
Purchase #5	$111.31	4.647%	$116.4826	$116.48	$116.50	$116.50
Purchase #6	$18.45	13.410%	$20.9241	$20.92	$20.90	$20.90
Purchase #7	$236.90	11.648%	$264.4941	$264.49	$264.50	$264.50
7 purchase totals =	$787.56		$853.6524	$853.64	$853.65	$853.70