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	$113.67	11.776%	$127.0558	$127.06	$127.05	$127.10
Purchase #2	$62.96	12.725%	$70.9717	$70.97	$70.95	$71.00
Purchase #3	$105.25	3.510%	$108.9443	$108.94	$108.95	$108.90
Purchase #4	$84.36	6.176%	$89.5701	$89.57	$89.55	$89.60
Purchase #5	$122.30	7.727%	$131.7501	$131.75	$131.75	$131.80
Purchase #6	$135.60	11.180%	$150.7601	$150.76	$150.75	$150.80
Purchase #7	$77.66	5.449%	$81.8917	$81.89	$81.90	$81.90
7 purchase totals =	$701.80		$760.9438	$760.94	$760.90	$761.10