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	$56.28	7.541%	$60.5241	$60.52	$60.50	$60.50
Purchase #2	$211.73	4.422%	$221.0927	$221.09	$221.10	$221.10
Purchase #3	$160.48	7.712%	$172.8562	$172.86	$172.85	$172.90
Purchase #4	$159.94	6.433%	$170.2289	$170.23	$170.25	$170.20
Purchase #5	$250.85	11.789%	$280.4227	$280.42	$280.40	$280.40
Purchase #6	$101.34	11.772%	$113.2697	$113.27	$113.25	$113.30
Purchase #7	$102.98	5.818%	$108.9714	$108.97	$108.95	$109.00
7 purchase totals =	$1,043.60		$1,127.3657	$1,127.36	$1,127.30	$1,127.40