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	$20.52	11.545%	$22.889	$22.89	$22.90	$22.90
Purchase #2	$207.54	3.825%	$215.4784	$215.48	$215.50	$215.50
Purchase #3	$238.56	8.664%	$259.2288	$259.23	$259.25	$259.20
Purchase #4	$217.89	10.379%	$240.5048	$240.50	$240.50	$240.50
Purchase #5	$26.99	5.287%	$28.417	$28.42	$28.40	$28.40
Purchase #6	$87.47	12.764%	$98.6347	$98.63	$98.65	$98.60
Purchase #7	$200.85	9.781%	$220.4951	$220.50	$220.50	$220.50
7 purchase totals =	$999.82		$1,085.6478	$1,085.65	$1,085.70	$1,085.60