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	$152.44	10.175%	$167.9508	$167.95	$167.95	$168.00
Purchase #2	$194.32	6.352%	$206.6632	$206.66	$206.65	$206.70
Purchase #3	$240.48	12.474%	$270.4775	$270.48	$270.50	$270.50
Purchase #4	$60.32	3.564%	$62.4698	$62.47	$62.45	$62.50
Purchase #5	$167.43	12.820%	$188.8945	$188.89	$188.90	$188.90
Purchase #6	$63.82	5.202%	$67.1399	$67.14	$67.15	$67.10
Purchase #7	$162.94	8.344%	$176.5357	$176.54	$176.55	$176.50
7 purchase totals =	$1,041.75		$1,140.1314	$1,140.13	$1,140.15	$1,140.20