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	$100.69	3.484%	$104.198	$104.20	$104.20	$104.20
Purchase #2	$244.47	9.859%	$268.5723	$268.57	$268.55	$268.60
Purchase #3	$156.63	6.279%	$166.4648	$166.46	$166.45	$166.50
Purchase #4	$10.37	7.856%	$11.1847	$11.18	$11.20	$11.20
Purchase #5	$151.45	8.571%	$164.4308	$164.43	$164.45	$164.40
Purchase #6	$190.66	5.151%	$200.4809	$200.48	$200.50	$200.50
Purchase #7	$176.69	7.837%	$190.5372	$190.54	$190.55	$190.50
7 purchase totals =	$1,030.96		$1,105.8687	$1,105.86	$1,105.90	$1,105.90