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	$179.47	11.583%	$200.258	$200.26	$200.25	$200.30
Purchase #2	$75.51	9.578%	$82.7423	$82.74	$82.75	$82.70
Purchase #3	$9.45	9.822%	$10.3782	$10.38	$10.40	$10.40
Purchase #4	$91.67	8.294%	$99.2731	$99.27	$99.25	$99.30
Purchase #5	$196.90	8.231%	$213.1068	$213.11	$213.10	$213.10
Purchase #6	$99.82	3.665%	$103.4784	$103.48	$103.50	$103.50
Purchase #7	$199.64	5.112%	$209.8456	$209.85	$209.85	$209.80
7 purchase totals =	$852.46		$919.0824	$919.09	$919.10	$919.10