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	$197.48	13.605%	$224.3472	$224.35	$224.35	$224.30
Purchase #2	$231.35	4.530%	$241.8302	$241.83	$241.85	$241.80
Purchase #3	$40.64	12.348%	$45.6582	$45.66	$45.65	$45.70
Purchase #4	$72.94	10.398%	$80.5243	$80.52	$80.50	$80.50
Purchase #5	$101.89	5.284%	$107.2739	$107.27	$107.25	$107.30
Purchase #6	$56.56	4.442%	$59.0724	$59.07	$59.05	$59.10
Purchase #7	$29.87	11.746%	$33.3785	$33.38	$33.40	$33.40
7 purchase totals =	$730.73		$792.0847	$792.08	$792.05	$792.10