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	$33.71	12.504%	$37.9251	$37.93	$37.95	$37.90
Purchase #2	$42.50	11.486%	$47.3816	$47.38	$47.40	$47.40
Purchase #3	$99.78	3.154%	$102.9271	$102.93	$102.95	$102.90
Purchase #4	$48.53	6.274%	$51.5748	$51.57	$51.55	$51.60
Purchase #5	$34.44	11.337%	$38.3445	$38.34	$38.35	$38.30
Purchase #6	$130.94	13.428%	$148.5226	$148.52	$148.50	$148.50
Purchase #7	$156.71	12.636%	$176.5119	$176.51	$176.50	$176.50
7 purchase totals =	$546.61		$603.1876	$603.18	$603.20	$603.10