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	$77.97	7.841%	$84.0836	$84.08	$84.10	$84.10
Purchase #2	$21.87	4.281%	$22.8063	$22.81	$22.80	$22.80
Purchase #3	$43.63	4.383%	$45.5423	$45.54	$45.55	$45.50
Purchase #4	$196.71	7.525%	$211.5124	$211.51	$211.50	$211.50
Purchase #5	$242.69	5.716%	$256.5622	$256.56	$256.55	$256.60
Purchase #6	$196.78	9.595%	$215.661	$215.66	$215.65	$215.70
Purchase #7	$42.89	3.134%	$44.2342	$44.23	$44.25	$44.20
7 purchase totals =	$822.54		$880.4020	$880.39	$880.40	$880.40