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	$86.34	12.483%	$97.1178	$97.12	$97.10	$97.10
Purchase #2	$106.77	11.312%	$118.8478	$118.85	$118.85	$118.80
Purchase #3	$134.44	11.673%	$150.1332	$150.13	$150.15	$150.10
Purchase #4	$167.57	6.619%	$178.6615	$178.66	$178.65	$178.70
Purchase #5	$64.59	12.257%	$72.5068	$72.51	$72.50	$72.50
Purchase #6	$65.47	10.136%	$72.106	$72.11	$72.10	$72.10
Purchase #7	$112.39	5.873%	$118.9907	$118.99	$119.00	$119.00
7 purchase totals =	$737.57		$808.3638	$808.37	$808.35	$808.30