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	$161.76	12.657%	$182.234	$182.23	$182.25	$182.20
Purchase #2	$80.93	11.225%	$90.0144	$90.01	$90.00	$90.00
Purchase #3	$146.32	6.295%	$155.5308	$155.53	$155.55	$155.50
Purchase #4	$10.60	4.813%	$11.1102	$11.11	$11.10	$11.10
Purchase #5	$145.58	13.266%	$164.8926	$164.89	$164.90	$164.90
Purchase #6	$175.25	13.696%	$199.2522	$199.25	$199.25	$199.30
Purchase #7	$44.87	12.420%	$50.4429	$50.44	$50.45	$50.40
7 purchase totals =	$765.31		$853.4771	$853.46	$853.50	$853.40