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	$87.87	9.589%	$96.2959	$96.30	$96.30	$96.30
Purchase #2	$180.43	11.134%	$200.5191	$200.52	$200.50	$200.50
Purchase #3	$100.41	10.135%	$110.5866	$110.59	$110.60	$110.60
Purchase #4	$233.90	5.181%	$246.0184	$246.02	$246.00	$246.00
Purchase #5	$236.98	9.479%	$259.4433	$259.44	$259.45	$259.40
Purchase #6	$50.60	3.257%	$52.248	$52.25	$52.25	$52.20
Purchase #7	$247.50	13.336%	$280.5066	$280.51	$280.50	$280.50
7 purchase totals =	$1,137.69		$1,245.6179	$1,245.63	$1,245.60	$1,245.50