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	$231.44	6.684%	$246.9094	$246.91	$246.90	$246.90
Purchase #2	$7.29	8.479%	$7.9081	$7.91	$7.90	$7.90
Purchase #3	$164.78	9.766%	$180.8724	$180.87	$180.85	$180.90
Purchase #4	$7.72	13.787%	$8.7844	$8.78	$8.80	$8.80
Purchase #5	$199.72	6.766%	$213.2331	$213.23	$213.25	$213.20
Purchase #6	$212.54	12.120%	$238.2998	$238.30	$238.30	$238.30
Purchase #7	$109.40	7.418%	$117.5153	$117.52	$117.50	$117.50
7 purchase totals =	$932.89		$1,013.5225	$1,013.52	$1,013.50	$1,013.50