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	$85.40	6.497%	$90.9484	$90.95	$90.95	$90.90
Purchase #2	$34.83	9.128%	$38.0093	$38.01	$38.00	$38.00
Purchase #3	$87.49	6.533%	$93.2057	$93.21	$93.20	$93.20
Purchase #4	$84.98	4.113%	$88.4752	$88.48	$88.50	$88.50
Purchase #5	$236.29	12.738%	$266.3886	$266.39	$266.40	$266.40
Purchase #6	$225.33	10.186%	$248.2821	$248.28	$248.30	$248.30
Purchase #7	$142.83	7.274%	$153.2195	$153.22	$153.20	$153.20
7 purchase totals =	$897.15		$978.5288	$978.54	$978.55	$978.50