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	$153.82	11.567%	$171.6124	$171.61	$171.60	$171.60
Purchase #2	$85.35	4.676%	$89.341	$89.34	$89.35	$89.30
Purchase #3	$47.59	13.483%	$54.0066	$54.01	$54.00	$54.00
Purchase #4	$237.93	12.374%	$267.3715	$267.37	$267.35	$267.40
Purchase #5	$97.59	6.491%	$103.9246	$103.92	$103.90	$103.90
Purchase #6	$156.83	4.833%	$164.4096	$164.41	$164.40	$164.40
Purchase #7	$147.94	11.482%	$164.9265	$164.93	$164.95	$164.90
7 purchase totals =	$927.05		$1,015.5922	$1,015.59	$1,015.55	$1,015.50