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	$227.31	7.153%	$243.5695	$243.57	$243.55	$243.60
Purchase #2	$82.98	13.713%	$94.359	$94.36	$94.35	$94.40
Purchase #3	$48.32	3.227%	$49.8793	$49.88	$49.90	$49.90
Purchase #4	$88.54	6.723%	$94.4925	$94.49	$94.50	$94.50
Purchase #5	$201.85	3.253%	$208.4162	$208.42	$208.40	$208.40
Purchase #6	$186.39	11.788%	$208.3617	$208.36	$208.35	$208.40
Purchase #7	$127.44	11.763%	$142.4308	$142.43	$142.45	$142.40
7 purchase totals =	$962.83		$1,041.5090	$1,041.51	$1,041.50	$1,041.60