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	$58.42	6.830%	$62.4101	$62.41	$62.40	$62.40
Purchase #2	$173.58	13.407%	$196.8519	$196.85	$196.85	$196.90
Purchase #3	$201.46	9.119%	$219.8311	$219.83	$219.85	$219.80
Purchase #4	$185.90	9.750%	$204.0253	$204.03	$204.05	$204.00
Purchase #5	$34.67	6.281%	$36.8476	$36.85	$36.85	$36.80
Purchase #6	$77.70	10.696%	$86.0108	$86.01	$86.00	$86.00
Purchase #7	$56.56	5.732%	$59.802	$59.80	$59.80	$59.80
7 purchase totals =	$788.29		$865.7788	$865.78	$865.80	$865.70