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	$158.87	9.197%	$173.4813	$173.48	$173.50	$173.50
Purchase #2	$33.85	5.108%	$35.5791	$35.58	$35.60	$35.60
Purchase #3	$240.68	10.799%	$266.671	$266.67	$266.65	$266.70
Purchase #4	$144.63	9.824%	$158.8385	$158.84	$158.85	$158.80
Purchase #5	$31.37	7.303%	$33.661	$33.66	$33.65	$33.70
Purchase #6	$224.97	8.107%	$243.2083	$243.21	$243.20	$243.20
Purchase #7	$144.50	5.293%	$152.1484	$152.15	$152.15	$152.10
7 purchase totals =	$978.87		$1,063.5876	$1,063.59	$1,063.60	$1,063.60