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	$117.64	8.454%	$127.5853	$127.59	$127.60	$127.60
Purchase #2	$190.77	3.187%	$196.8498	$196.85	$196.85	$196.80
Purchase #3	$39.91	5.441%	$42.0815	$42.08	$42.10	$42.10
Purchase #4	$243.49	9.248%	$266.008	$266.01	$266.00	$266.00
Purchase #5	$65.61	10.502%	$72.5004	$72.50	$72.50	$72.50
Purchase #6	$134.45	10.676%	$148.8039	$148.80	$148.80	$148.80
Purchase #7	$210.63	5.496%	$222.2062	$222.21	$222.20	$222.20
7 purchase totals =	$1,002.50		$1,076.0351	$1,076.04	$1,076.05	$1,076.00