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	$197.51	7.243%	$211.8156	$211.82	$211.80	$211.80
Purchase #2	$75.61	4.340%	$78.8915	$78.89	$78.90	$78.90
Purchase #3	$35.59	11.821%	$39.7971	$39.80	$39.80	$39.80
Purchase #4	$160.74	3.588%	$166.5074	$166.51	$166.50	$166.50
Purchase #5	$123.49	12.436%	$138.8472	$138.85	$138.85	$138.80
Purchase #6	$142.30	7.504%	$152.9782	$152.98	$153.00	$153.00
Purchase #7	$222.76	6.396%	$237.0077	$237.01	$237.00	$237.00
7 purchase totals =	$958.00		$1,025.8447	$1,025.86	$1,025.85	$1,025.80