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	$225.96	9.575%	$247.5957	$247.60	$247.60	$247.60
Purchase #2	$236.86	9.460%	$259.267	$259.27	$259.25	$259.30
Purchase #3	$57.84	12.761%	$65.221	$65.22	$65.20	$65.20
Purchase #4	$215.94	6.193%	$229.3132	$229.31	$229.30	$229.30
Purchase #5	$17.79	3.667%	$18.4424	$18.44	$18.45	$18.40
Purchase #6	$186.64	12.420%	$209.8207	$209.82	$209.80	$209.80
Purchase #7	$37.95	11.859%	$42.4505	$42.45	$42.45	$42.50
7 purchase totals =	$978.98		$1,072.1105	$1,072.11	$1,072.05	$1,072.10