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	$248.44	10.317%	$274.0716	$274.07	$274.05	$274.10
Purchase #2	$146.57	3.707%	$152.0033	$152.00	$152.00	$152.00
Purchase #3	$65.44	3.135%	$67.4915	$67.49	$67.50	$67.50
Purchase #4	$196.44	12.155%	$220.3173	$220.32	$220.30	$220.30
Purchase #5	$179.44	10.694%	$198.6293	$198.63	$198.65	$198.60
Purchase #6	$49.48	10.803%	$54.8253	$54.83	$54.85	$54.80
Purchase #7	$33.78	11.310%	$37.6005	$37.60	$37.60	$37.60
7 purchase totals =	$919.59		$1,004.9388	$1,004.94	$1,004.95	$1,004.90