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	$86.66	8.544%	$94.0642	$94.06	$94.05	$94.10
Purchase #2	$109.34	3.228%	$112.8695	$112.87	$112.85	$112.90
Purchase #3	$178.91	12.827%	$201.8588	$201.86	$201.85	$201.90
Purchase #4	$50.38	10.332%	$55.5853	$55.59	$55.60	$55.60
Purchase #5	$187.76	4.676%	$196.5397	$196.54	$196.55	$196.50
Purchase #6	$139.54	4.736%	$146.1486	$146.15	$146.15	$146.10
Purchase #7	$155.70	9.467%	$170.4401	$170.44	$170.45	$170.40
7 purchase totals =	$908.29		$977.5062	$977.51	$977.50	$977.50