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	$139.65	9.410%	$152.7911	$152.79	$152.80	$152.80
Purchase #2	$75.82	13.480%	$86.0405	$86.04	$86.05	$86.00
Purchase #3	$45.66	3.809%	$47.3992	$47.40	$47.40	$47.40
Purchase #4	$131.33	13.168%	$148.6235	$148.62	$148.60	$148.60
Purchase #5	$24.85	13.693%	$28.2527	$28.25	$28.25	$28.30
Purchase #6	$140.27	8.770%	$152.5717	$152.57	$152.55	$152.60
Purchase #7	$247.25	13.687%	$281.0911	$281.09	$281.10	$281.10
7 purchase totals =	$804.83		$896.7698	$896.76	$896.75	$896.80