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	$171.75	13.198%	$194.4176	$194.42	$194.40	$194.40
Purchase #2	$176.98	7.637%	$190.496	$190.50	$190.50	$190.50
Purchase #3	$27.68	10.332%	$30.5399	$30.54	$30.55	$30.50
Purchase #4	$28.82	12.633%	$32.4608	$32.46	$32.45	$32.50
Purchase #5	$37.68	13.850%	$42.8987	$42.90	$42.90	$42.90
Purchase #6	$163.77	6.509%	$174.4298	$174.43	$174.45	$174.40
Purchase #7	$129.77	9.112%	$141.5946	$141.59	$141.60	$141.60
7 purchase totals =	$736.45		$806.8374	$806.84	$806.85	$806.80