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	$200.58	11.198%	$223.0409	$223.04	$223.05	$223.00
Purchase #2	$207.47	10.621%	$229.5054	$229.51	$229.50	$229.50
Purchase #3	$18.98	10.475%	$20.9682	$20.97	$20.95	$21.00
Purchase #4	$155.27	10.306%	$171.2721	$171.27	$171.25	$171.30
Purchase #5	$98.64	6.676%	$105.2252	$105.23	$105.25	$105.20
Purchase #6	$159.30	8.156%	$172.2925	$172.29	$172.30	$172.30
Purchase #7	$13.57	11.201%	$15.09	$15.09	$15.10	$15.10
7 purchase totals =	$853.81		$937.3943	$937.40	$937.40	$937.40