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	$51.58	11.746%	$57.6386	$57.64	$57.65	$57.60
Purchase #2	$66.37	10.355%	$73.2426	$73.24	$73.25	$73.20
Purchase #3	$34.38	9.285%	$37.5722	$37.57	$37.55	$37.60
Purchase #4	$237.99	12.386%	$267.4674	$267.47	$267.45	$267.50
Purchase #5	$86.72	4.363%	$90.5036	$90.50	$90.50	$90.50
Purchase #6	$147.47	10.642%	$163.1638	$163.16	$163.15	$163.20
Purchase #7	$89.61	8.132%	$96.8971	$96.90	$96.90	$96.90
7 purchase totals =	$714.12		$786.4853	$786.48	$786.45	$786.50