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	$105.27	12.609%	$118.5435	$118.54	$118.55	$118.50
Purchase #2	$98.27	9.478%	$107.584	$107.58	$107.60	$107.60
Purchase #3	$75.79	13.853%	$86.2892	$86.29	$86.30	$86.30
Purchase #4	$144.83	13.597%	$164.5225	$164.52	$164.50	$164.50
Purchase #5	$137.37	9.595%	$150.5507	$150.55	$150.55	$150.60
Purchase #6	$67.32	3.738%	$69.8364	$69.84	$69.85	$69.80
Purchase #7	$243.38	13.536%	$276.3239	$276.32	$276.30	$276.30
7 purchase totals =	$872.23		$973.6502	$973.64	$973.65	$973.60