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	$82.79	5.731%	$87.5347	$87.53	$87.55	$87.50
Purchase #2	$26.82	4.311%	$27.9762	$27.98	$28.00	$28.00
Purchase #3	$145.43	7.826%	$156.8114	$156.81	$156.80	$156.80
Purchase #4	$188.76	6.211%	$200.4839	$200.48	$200.50	$200.50
Purchase #5	$190.52	10.698%	$210.9018	$210.90	$210.90	$210.90
Purchase #6	$123.81	3.332%	$127.9353	$127.94	$127.95	$127.90
Purchase #7	$65.48	11.127%	$72.766	$72.77	$72.75	$72.80
7 purchase totals =	$823.61		$884.4093	$884.41	$884.45	$884.40