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	$246.43	3.611%	$255.3286	$255.33	$255.35	$255.30
Purchase #2	$81.39	8.470%	$88.2837	$88.28	$88.30	$88.30
Purchase #3	$113.56	8.414%	$123.1149	$123.11	$123.10	$123.10
Purchase #4	$216.27	11.338%	$240.7907	$240.79	$240.80	$240.80
Purchase #5	$87.60	8.420%	$94.9759	$94.98	$95.00	$95.00
Purchase #6	$168.44	10.142%	$185.5232	$185.52	$185.50	$185.50
Purchase #7	$196.74	7.756%	$211.9992	$212.00	$212.00	$212.00
7 purchase totals =	$1,110.43		$1,200.0162	$1,200.01	$1,200.05	$1,200.00