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	$198.63	13.702%	$225.8463	$225.85	$225.85	$225.80
Purchase #2	$89.59	7.647%	$96.4409	$96.44	$96.45	$96.40
Purchase #3	$160.41	3.204%	$165.5495	$165.55	$165.55	$165.50
Purchase #4	$182.99	8.801%	$199.0949	$199.09	$199.10	$199.10
Purchase #5	$134.57	7.638%	$144.8485	$144.85	$144.85	$144.80
Purchase #6	$88.77	10.699%	$98.2675	$98.27	$98.25	$98.30
Purchase #7	$112.46	4.797%	$117.8547	$117.85	$117.85	$117.90
7 purchase totals =	$967.42		$1,047.9023	$1,047.90	$1,047.90	$1,047.80