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	$82.79	7.583%	$89.068	$89.07	$89.05	$89.10
Purchase #2	$174.56	11.464%	$194.5716	$194.57	$194.55	$194.60
Purchase #3	$196.98	5.863%	$208.5289	$208.53	$208.55	$208.50
Purchase #4	$160.25	4.842%	$168.0093	$168.01	$168.00	$168.00
Purchase #5	$173.68	10.377%	$191.7028	$191.70	$191.70	$191.70
Purchase #6	$83.83	13.854%	$95.4438	$95.44	$95.45	$95.40
Purchase #7	$244.57	7.570%	$263.0839	$263.08	$263.10	$263.10
7 purchase totals =	$1,116.66		$1,210.4083	$1,210.40	$1,210.40	$1,210.40