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	$151.78	3.276%	$156.7523	$156.75	$156.75	$156.80
Purchase #2	$75.74	6.402%	$80.5889	$80.59	$80.60	$80.60
Purchase #3	$85.30	6.210%	$90.5971	$90.60	$90.60	$90.60
Purchase #4	$147.31	6.422%	$156.7702	$156.77	$156.75	$156.80
Purchase #5	$88.58	4.161%	$92.2658	$92.27	$92.25	$92.30
Purchase #6	$86.85	10.530%	$95.9953	$96.00	$96.00	$96.00
Purchase #7	$199.94	11.411%	$222.7552	$222.76	$222.75	$222.80
7 purchase totals =	$835.50		$895.7248	$895.74	$895.70	$895.90