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	$158.95	3.530%	$164.5609	$164.56	$164.55	$164.60
Purchase #2	$5.84	12.787%	$6.5868	$6.59	$6.60	$6.60
Purchase #3	$89.54	13.568%	$101.6888	$101.69	$101.70	$101.70
Purchase #4	$244.80	4.459%	$255.7156	$255.72	$255.70	$255.70
Purchase #5	$204.51	10.694%	$226.3803	$226.38	$226.40	$226.40
Purchase #6	$81.76	4.438%	$85.3885	$85.39	$85.40	$85.40
Purchase #7	$125.35	13.696%	$142.5179	$142.52	$142.50	$142.50
7 purchase totals =	$910.75		$982.8388	$982.85	$982.85	$982.90