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	$43.57	3.823%	$45.2357	$45.24	$45.25	$45.20
Purchase #2	$150.35	10.331%	$165.8827	$165.88	$165.90	$165.90
Purchase #3	$101.44	3.750%	$105.244	$105.24	$105.25	$105.20
Purchase #4	$187.89	12.467%	$211.3142	$211.31	$211.30	$211.30
Purchase #5	$231.69	11.440%	$258.1953	$258.20	$258.20	$258.20
Purchase #6	$104.38	11.104%	$115.9704	$115.97	$115.95	$116.00
Purchase #7	$90.84	5.301%	$95.6554	$95.66	$95.65	$95.70
7 purchase totals =	$910.16		$997.4977	$997.50	$997.50	$997.50