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	$200.47	3.167%	$206.8189	$206.82	$206.80	$206.80
Purchase #2	$190.64	5.688%	$201.4836	$201.48	$201.50	$201.50
Purchase #3	$198.79	11.869%	$222.3844	$222.38	$222.40	$222.40
Purchase #4	$72.76	7.708%	$78.3683	$78.37	$78.35	$78.40
Purchase #5	$187.87	11.590%	$209.6441	$209.64	$209.65	$209.60
Purchase #6	$188.48	5.354%	$198.5712	$198.57	$198.55	$198.60
Purchase #7	$153.88	11.619%	$171.7593	$171.76	$171.75	$171.80
7 purchase totals =	$1,192.89		$1,289.0298	$1,289.02	$1,289.00	$1,289.10