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	$151.35	6.332%	$160.9335	$160.93	$160.95	$160.90
Purchase #2	$60.96	8.649%	$66.2324	$66.23	$66.25	$66.20
Purchase #3	$74.69	10.564%	$82.5803	$82.58	$82.60	$82.60
Purchase #4	$171.29	12.807%	$193.2271	$193.23	$193.25	$193.20
Purchase #5	$147.96	11.264%	$164.6262	$164.63	$164.65	$164.60
Purchase #6	$77.78	5.697%	$82.2111	$82.21	$82.20	$82.20
Purchase #7	$152.81	10.163%	$168.3401	$168.34	$168.35	$168.30
7 purchase totals =	$836.84		$918.1507	$918.15	$918.25	$918.00