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	$213.52	4.382%	$222.8764	$222.88	$222.90	$222.90
Purchase #2	$128.35	9.343%	$140.3417	$140.34	$140.35	$140.30
Purchase #3	$243.53	6.569%	$259.5275	$259.53	$259.55	$259.50
Purchase #4	$103.70	10.475%	$114.5626	$114.56	$114.55	$114.60
Purchase #5	$60.32	13.234%	$68.3027	$68.30	$68.30	$68.30
Purchase #6	$236.96	8.209%	$256.412	$256.41	$256.40	$256.40
Purchase #7	$71.36	9.874%	$78.4061	$78.41	$78.40	$78.40
7 purchase totals =	$1,057.74		$1,140.4290	$1,140.43	$1,140.45	$1,140.40