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	$216.63	5.321%	$228.1569	$228.16	$228.15	$228.20
Purchase #2	$184.43	6.693%	$196.7739	$196.77	$196.75	$196.80
Purchase #3	$119.48	7.550%	$128.5007	$128.50	$128.50	$128.50
Purchase #4	$228.69	13.528%	$259.6272	$259.63	$259.65	$259.60
Purchase #5	$112.94	12.360%	$126.8994	$126.90	$126.90	$126.90
Purchase #6	$103.76	3.473%	$107.3636	$107.36	$107.35	$107.40
Purchase #7	$111.29	13.730%	$126.5701	$126.57	$126.55	$126.60
7 purchase totals =	$1,077.22		$1,173.8918	$1,173.89	$1,173.85	$1,174.00