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	$208.70	13.443%	$236.7555	$236.76	$236.75	$236.80
Purchase #2	$220.76	11.787%	$246.781	$246.78	$246.80	$246.80
Purchase #3	$189.47	3.579%	$196.2511	$196.25	$196.25	$196.30
Purchase #4	$83.33	4.263%	$86.8824	$86.88	$86.90	$86.90
Purchase #5	$29.90	7.312%	$32.0863	$32.09	$32.10	$32.10
Purchase #6	$139.76	10.411%	$154.3104	$154.31	$154.30	$154.30
Purchase #7	$206.63	7.791%	$222.7285	$222.73	$222.75	$222.70
7 purchase totals =	$1,078.55		$1,175.7952	$1,175.80	$1,175.85	$1,175.90