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	$39.63	3.537%	$41.0317	$41.03	$41.05	$41.00
Purchase #2	$52.79	12.775%	$59.5339	$59.53	$59.55	$59.50
Purchase #3	$156.39	7.540%	$168.1818	$168.18	$168.20	$168.20
Purchase #4	$55.74	6.695%	$59.4718	$59.47	$59.45	$59.50
Purchase #5	$87.61	10.577%	$96.8765	$96.88	$96.90	$96.90
Purchase #6	$116.50	7.246%	$124.9416	$124.94	$124.95	$124.90
Purchase #7	$163.35	12.213%	$183.2999	$183.30	$183.30	$183.30
7 purchase totals =	$672.01		$733.3372	$733.33	$733.40	$733.30