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	$222.85	7.560%	$239.6975	$239.70	$239.70	$239.70
Purchase #2	$188.64	4.342%	$196.8307	$196.83	$196.85	$196.80
Purchase #3	$31.36	8.199%	$33.9312	$33.93	$33.95	$33.90
Purchase #4	$157.77	10.647%	$174.5678	$174.57	$174.55	$174.60
Purchase #5	$198.69	7.314%	$213.2222	$213.22	$213.20	$213.20
Purchase #6	$87.39	3.662%	$90.5902	$90.59	$90.60	$90.60
Purchase #7	$112.65	6.577%	$120.059	$120.06	$120.05	$120.10
7 purchase totals =	$999.35		$1,068.8986	$1,068.90	$1,068.90	$1,068.90