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	$184.81	6.569%	$196.9502	$196.95	$196.95	$197.00
Purchase #2	$155.85	12.384%	$175.1505	$175.15	$175.15	$175.20
Purchase #3	$197.32	6.384%	$209.9169	$209.92	$209.90	$209.90
Purchase #4	$6.87	12.847%	$7.7526	$7.75	$7.75	$7.80
Purchase #5	$86.31	6.194%	$91.656	$91.66	$91.65	$91.70
Purchase #6	$161.86	12.688%	$182.3968	$182.40	$182.40	$182.40
Purchase #7	$80.34	12.659%	$90.5102	$90.51	$90.50	$90.50
7 purchase totals =	$873.36		$954.3332	$954.34	$954.30	$954.50