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	$233.54	5.551%	$246.5038	$246.50	$246.50	$246.50
Purchase #2	$77.27	5.362%	$81.4132	$81.41	$81.40	$81.40
Purchase #3	$217.48	12.719%	$245.1413	$245.14	$245.15	$245.10
Purchase #4	$41.65	8.782%	$45.3077	$45.31	$45.30	$45.30
Purchase #5	$234.45	6.156%	$248.8827	$248.88	$248.90	$248.90
Purchase #6	$182.78	4.382%	$190.7894	$190.79	$190.80	$190.80
Purchase #7	$236.73	7.801%	$255.1973	$255.20	$255.20	$255.20
7 purchase totals =	$1,223.90		$1,313.2354	$1,313.23	$1,313.25	$1,313.20