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	$185.51	10.587%	$205.1499	$205.15	$205.15	$205.10
Purchase #2	$215.89	12.825%	$243.5779	$243.58	$243.60	$243.60
Purchase #3	$168.37	6.767%	$179.7636	$179.76	$179.75	$179.80
Purchase #4	$98.75	11.778%	$110.3808	$110.38	$110.40	$110.40
Purchase #5	$181.95	8.249%	$196.9591	$196.96	$196.95	$197.00
Purchase #6	$86.93	9.439%	$95.1353	$95.14	$95.15	$95.10
Purchase #7	$38.27	13.871%	$43.5784	$43.58	$43.60	$43.60
7 purchase totals =	$975.67		$1,074.5450	$1,074.55	$1,074.60	$1,074.60