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	$177.67	9.242%	$194.0903	$194.09	$194.10	$194.10
Purchase #2	$67.71	7.724%	$72.9399	$72.94	$72.95	$72.90
Purchase #3	$5.33	4.396%	$5.5643	$5.56	$5.55	$5.60
Purchase #4	$103.59	5.310%	$109.0906	$109.09	$109.10	$109.10
Purchase #5	$237.28	4.483%	$247.9173	$247.92	$247.90	$247.90
Purchase #6	$129.42	10.381%	$142.8551	$142.86	$142.85	$142.90
Purchase #7	$135.52	5.601%	$143.1105	$143.11	$143.10	$143.10
7 purchase totals =	$856.52		$915.5680	$915.57	$915.55	$915.60