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	$43.61	8.266%	$47.2148	$47.21	$47.20	$47.20
Purchase #2	$145.89	12.691%	$164.4049	$164.40	$164.40	$164.40
Purchase #3	$124.94	7.531%	$134.3492	$134.35	$134.35	$134.30
Purchase #4	$248.54	5.159%	$261.3622	$261.36	$261.35	$261.40
Purchase #5	$27.69	9.560%	$30.3372	$30.34	$30.35	$30.30
Purchase #6	$159.98	5.223%	$168.3358	$168.34	$168.35	$168.30
Purchase #7	$245.67	3.833%	$255.0865	$255.09	$255.10	$255.10
7 purchase totals =	$996.32		$1,061.0906	$1,061.09	$1,061.10	$1,061.00