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	$10.72	6.558%	$11.423	$11.42	$11.40	$11.40
Purchase #2	$144.29	5.541%	$152.2851	$152.29	$152.30	$152.30
Purchase #3	$159.25	5.864%	$168.5884	$168.59	$168.60	$168.60
Purchase #4	$221.66	8.262%	$239.9735	$239.97	$239.95	$240.00
Purchase #5	$165.53	8.288%	$179.2491	$179.25	$179.25	$179.20
Purchase #6	$248.29	11.283%	$276.3046	$276.30	$276.30	$276.30
Purchase #7	$205.28	10.789%	$227.4277	$227.43	$227.45	$227.40
7 purchase totals =	$1,155.02		$1,255.2514	$1,255.25	$1,255.25	$1,255.20