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	$102.81	5.638%	$108.6064	$108.61	$108.60	$108.60
Purchase #2	$127.99	6.614%	$136.4553	$136.46	$136.45	$136.50
Purchase #3	$158.86	13.562%	$180.4046	$180.40	$180.40	$180.40
Purchase #4	$211.82	7.364%	$227.4184	$227.42	$227.40	$227.40
Purchase #5	$152.96	4.651%	$160.0742	$160.07	$160.05	$160.10
Purchase #6	$240.33	13.494%	$272.7601	$272.76	$272.75	$272.80
Purchase #7	$123.61	6.467%	$131.6039	$131.60	$131.60	$131.60
7 purchase totals =	$1,118.38		$1,217.3229	$1,217.32	$1,217.25	$1,217.40