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	$75.59	10.188%	$83.2911	$83.29	$83.30	$83.30
Purchase #2	$20.43	10.760%	$22.6283	$22.63	$22.65	$22.60
Purchase #3	$121.78	3.873%	$126.4965	$126.50	$126.50	$126.50
Purchase #4	$29.37	10.134%	$32.3464	$32.35	$32.35	$32.30
Purchase #5	$12.59	11.765%	$14.0712	$14.07	$14.05	$14.10
Purchase #6	$80.96	6.286%	$86.0491	$86.05	$86.05	$86.00
Purchase #7	$82.83	9.483%	$90.6848	$90.68	$90.70	$90.70
7 purchase totals =	$423.55		$455.5674	$455.57	$455.60	$455.50