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	$104.33	7.849%	$112.5189	$112.52	$112.50	$112.50
Purchase #2	$100.92	8.522%	$109.5204	$109.52	$109.50	$109.50
Purchase #3	$190.51	3.211%	$196.6273	$196.63	$196.65	$196.60
Purchase #4	$88.89	5.611%	$93.8776	$93.88	$93.90	$93.90
Purchase #5	$108.34	9.696%	$118.8446	$118.84	$118.85	$118.80
Purchase #6	$93.88	4.493%	$98.098	$98.10	$98.10	$98.10
Purchase #7	$23.49	6.662%	$25.0549	$25.05	$25.05	$25.10
7 purchase totals =	$710.36		$754.5417	$754.54	$754.55	$754.50