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	$87.34	5.218%	$91.8974	$91.90	$91.90	$91.90
Purchase #2	$74.34	5.349%	$78.3164	$78.32	$78.30	$78.30
Purchase #3	$131.92	4.282%	$137.5688	$137.57	$137.55	$137.60
Purchase #4	$211.59	3.728%	$219.4781	$219.48	$219.50	$219.50
Purchase #5	$166.99	9.822%	$183.3918	$183.39	$183.40	$183.40
Purchase #6	$59.97	9.242%	$65.5124	$65.51	$65.50	$65.50
Purchase #7	$143.53	4.509%	$150.0018	$150.00	$150.00	$150.00
7 purchase totals =	$875.68		$926.1667	$926.17	$926.15	$926.20