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	$208.66	3.489%	$215.9401	$215.94	$215.95	$215.90
Purchase #2	$99.37	3.815%	$103.161	$103.16	$103.15	$103.20
Purchase #3	$200.66	13.222%	$227.1913	$227.19	$227.20	$227.20
Purchase #4	$120.86	8.597%	$131.2503	$131.25	$131.25	$131.30
Purchase #5	$90.49	12.810%	$102.0818	$102.08	$102.10	$102.10
Purchase #6	$235.63	7.663%	$253.6863	$253.69	$253.70	$253.70
Purchase #7	$12.58	12.114%	$14.1039	$14.10	$14.10	$14.10
7 purchase totals =	$968.25		$1,047.4147	$1,047.41	$1,047.45	$1,047.50