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	$84.65	11.868%	$94.6963	$94.70	$94.70	$94.70
Purchase #2	$89.46	3.260%	$92.3764	$92.38	$92.40	$92.40
Purchase #3	$138.33	9.527%	$151.5087	$151.51	$151.50	$151.50
Purchase #4	$243.88	12.517%	$274.4065	$274.41	$274.40	$274.40
Purchase #5	$226.62	7.587%	$243.8137	$243.81	$243.80	$243.80
Purchase #6	$112.69	3.160%	$116.251	$116.25	$116.25	$116.30
Purchase #7	$107.59	3.666%	$111.5342	$111.53	$111.55	$111.50
7 purchase totals =	$1,003.22		$1,084.5868	$1,084.59	$1,084.60	$1,084.60