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	$220.82	8.182%	$238.8875	$238.89	$238.90	$238.90
Purchase #2	$78.78	8.224%	$85.2589	$85.26	$85.25	$85.30
Purchase #3	$129.98	6.535%	$138.4742	$138.47	$138.45	$138.50
Purchase #4	$76.67	13.274%	$86.8472	$86.85	$86.85	$86.80
Purchase #5	$211.28	9.458%	$231.2629	$231.26	$231.25	$231.30
Purchase #6	$198.60	5.538%	$209.5985	$209.60	$209.60	$209.60
Purchase #7	$189.68	8.722%	$206.2239	$206.22	$206.20	$206.20
7 purchase totals =	$1,105.81		$1,196.5531	$1,196.55	$1,196.50	$1,196.60