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	$196.77	8.690%	$213.8693	$213.87	$213.85	$213.90
Purchase #2	$221.32	6.837%	$236.4516	$236.45	$236.45	$236.50
Purchase #3	$89.94	12.699%	$101.3615	$101.36	$101.35	$101.40
Purchase #4	$225.96	3.520%	$233.9138	$233.91	$233.90	$233.90
Purchase #5	$37.42	8.633%	$40.6505	$40.65	$40.65	$40.70
Purchase #6	$66.51	9.573%	$72.877	$72.88	$72.90	$72.90
Purchase #7	$77.84	3.445%	$80.5216	$80.52	$80.50	$80.50
7 purchase totals =	$915.76		$979.6453	$979.64	$979.60	$979.80