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	$144.98	7.574%	$155.9608	$155.96	$155.95	$156.00
Purchase #2	$243.29	7.522%	$261.5903	$261.59	$261.60	$261.60
Purchase #3	$10.37	7.825%	$11.1815	$11.18	$11.20	$11.20
Purchase #4	$142.69	9.707%	$156.5409	$156.54	$156.55	$156.50
Purchase #5	$240.82	12.518%	$270.9658	$270.97	$270.95	$271.00
Purchase #6	$132.76	6.284%	$141.1026	$141.10	$141.10	$141.10
Purchase #7	$169.93	9.214%	$185.5874	$185.59	$185.60	$185.60
7 purchase totals =	$1,084.84		$1,182.9293	$1,182.93	$1,182.95	$1,183.00