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	$82.78	3.531%	$85.703	$85.70	$85.70	$85.70
Purchase #2	$147.90	7.609%	$159.1537	$159.15	$159.15	$159.20
Purchase #3	$133.87	4.319%	$139.6518	$139.65	$139.65	$139.70
Purchase #4	$92.59	11.818%	$103.5323	$103.53	$103.55	$103.50
Purchase #5	$100.48	13.591%	$114.1362	$114.14	$114.15	$114.10
Purchase #6	$62.92	5.249%	$66.2227	$66.22	$66.20	$66.20
Purchase #7	$34.87	13.372%	$39.5328	$39.53	$39.55	$39.50
7 purchase totals =	$655.41		$707.9325	$707.92	$707.95	$707.90