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	$216.56	8.472%	$234.907	$234.91	$234.90	$234.90
Purchase #2	$211.29	3.287%	$218.2351	$218.24	$218.25	$218.20
Purchase #3	$177.29	4.691%	$185.6067	$185.61	$185.60	$185.60
Purchase #4	$60.39	11.840%	$67.5402	$67.54	$67.55	$67.50
Purchase #5	$133.48	10.558%	$147.5728	$147.57	$147.55	$147.60
Purchase #6	$67.64	3.286%	$69.8627	$69.86	$69.85	$69.90
Purchase #7	$72.51	11.465%	$80.8233	$80.82	$80.80	$80.80
7 purchase totals =	$939.16		$1,004.5478	$1,004.55	$1,004.50	$1,004.50