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	$240.95	7.549%	$259.1393	$259.14	$259.15	$259.10
Purchase #2	$141.26	3.726%	$146.5233	$146.52	$146.50	$146.50
Purchase #3	$215.98	4.551%	$225.8092	$225.81	$225.80	$225.80
Purchase #4	$87.46	12.410%	$98.3138	$98.31	$98.30	$98.30
Purchase #5	$94.38	7.607%	$101.5595	$101.56	$101.55	$101.60
Purchase #6	$88.82	5.807%	$93.9778	$93.98	$94.00	$94.00
Purchase #7	$126.65	10.425%	$139.8533	$139.85	$139.85	$139.90
7 purchase totals =	$995.50		$1,065.1762	$1,065.17	$1,065.15	$1,065.20