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	$199.76	9.136%	$218.0101	$218.01	$218.00	$218.00
Purchase #2	$82.37	9.859%	$90.4909	$90.49	$90.50	$90.50
Purchase #3	$167.96	4.541%	$175.5871	$175.59	$175.60	$175.60
Purchase #4	$142.90	8.778%	$155.4438	$155.44	$155.45	$155.40
Purchase #5	$246.99	3.663%	$256.0372	$256.04	$256.05	$256.00
Purchase #6	$50.73	8.760%	$55.1739	$55.17	$55.15	$55.20
Purchase #7	$74.34	5.626%	$78.5224	$78.52	$78.50	$78.50
7 purchase totals =	$965.05		$1,029.2654	$1,029.26	$1,029.25	$1,029.20