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	$90.93	5.192%	$95.6511	$95.65	$95.65	$95.70
Purchase #2	$128.50	4.600%	$134.411	$134.41	$134.40	$134.40
Purchase #3	$54.51	8.865%	$59.3423	$59.34	$59.35	$59.30
Purchase #4	$133.90	13.666%	$152.1988	$152.20	$152.20	$152.20
Purchase #5	$52.45	3.427%	$54.2475	$54.25	$54.25	$54.20
Purchase #6	$21.76	7.591%	$23.4118	$23.41	$23.40	$23.40
Purchase #7	$90.40	11.207%	$100.5311	$100.53	$100.55	$100.50
7 purchase totals =	$572.45		$619.7936	$619.79	$619.80	$619.70