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	$128.51	9.689%	$140.9613	$140.96	$140.95	$141.00
Purchase #2	$61.53	10.554%	$68.0239	$68.02	$68.00	$68.00
Purchase #3	$199.31	7.141%	$213.5427	$213.54	$213.55	$213.50
Purchase #4	$139.32	13.451%	$158.0599	$158.06	$158.05	$158.10
Purchase #5	$40.89	11.320%	$45.5187	$45.52	$45.50	$45.50
Purchase #6	$82.44	3.247%	$85.1168	$85.12	$85.10	$85.10
Purchase #7	$124.47	12.801%	$140.4034	$140.40	$140.40	$140.40
7 purchase totals =	$776.47		$851.6267	$851.62	$851.55	$851.60