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	$31.33	12.463%	$35.2347	$35.23	$35.25	$35.20
Purchase #2	$11.75	5.202%	$12.3612	$12.36	$12.35	$12.40
Purchase #3	$87.27	3.537%	$90.3567	$90.36	$90.35	$90.40
Purchase #4	$29.89	5.857%	$31.6407	$31.64	$31.65	$31.60
Purchase #5	$228.47	6.356%	$242.9916	$242.99	$243.00	$243.00
Purchase #6	$143.64	10.317%	$158.4593	$158.46	$158.45	$158.50
Purchase #7	$206.84	3.373%	$213.8167	$213.82	$213.80	$213.80
7 purchase totals =	$739.19		$784.8609	$784.86	$784.85	$784.90