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	$228.34	13.840%	$259.9423	$259.94	$259.95	$259.90
Purchase #2	$14.72	4.676%	$15.4083	$15.41	$15.40	$15.40
Purchase #3	$117.55	4.802%	$123.1948	$123.19	$123.20	$123.20
Purchase #4	$114.46	8.695%	$124.4123	$124.41	$124.40	$124.40
Purchase #5	$197.41	6.590%	$210.4193	$210.42	$210.40	$210.40
Purchase #6	$198.51	13.183%	$224.6796	$224.68	$224.70	$224.70
Purchase #7	$63.83	13.526%	$72.4636	$72.46	$72.45	$72.50
7 purchase totals =	$934.82		$1,030.5202	$1,030.51	$1,030.50	$1,030.50