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	$66.59	8.558%	$72.2888	$72.29	$72.30	$72.30
Purchase #2	$179.50	9.593%	$196.7194	$196.72	$196.70	$196.70
Purchase #3	$59.47	13.299%	$67.3789	$67.38	$67.40	$67.40
Purchase #4	$175.29	4.102%	$182.4804	$182.48	$182.50	$182.50
Purchase #5	$100.29	6.807%	$107.1167	$107.12	$107.10	$107.10
Purchase #6	$246.31	6.143%	$261.4408	$261.44	$261.45	$261.40
Purchase #7	$248.76	11.536%	$277.457	$277.46	$277.45	$277.50
7 purchase totals =	$1,076.21		$1,164.8820	$1,164.89	$1,164.90	$1,164.90