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	$233.93	12.295%	$262.6917	$262.69	$262.70	$262.70
Purchase #2	$112.58	4.410%	$117.5448	$117.54	$117.55	$117.50
Purchase #3	$200.79	4.333%	$209.4902	$209.49	$209.50	$209.50
Purchase #4	$169.34	9.181%	$184.8871	$184.89	$184.90	$184.90
Purchase #5	$98.72	13.353%	$111.9021	$111.90	$111.90	$111.90
Purchase #6	$224.85	11.400%	$250.4829	$250.48	$250.50	$250.50
Purchase #7	$126.75	7.575%	$136.3513	$136.35	$136.35	$136.40
7 purchase totals =	$1,166.96		$1,273.3501	$1,273.34	$1,273.40	$1,273.40