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	$81.85	4.350%	$85.4105	$85.41	$85.40	$85.40
Purchase #2	$94.46	8.367%	$102.3635	$102.36	$102.35	$102.40
Purchase #3	$241.38	13.651%	$274.3308	$274.33	$274.35	$274.30
Purchase #4	$113.71	8.840%	$123.762	$123.76	$123.75	$123.80
Purchase #5	$111.32	4.659%	$116.5064	$116.51	$116.50	$116.50
Purchase #6	$240.91	9.551%	$263.9193	$263.92	$263.90	$263.90
Purchase #7	$121.94	13.120%	$137.9385	$137.94	$137.95	$137.90
7 purchase totals =	$1,005.57		$1,104.2310	$1,104.23	$1,104.20	$1,104.20