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	$205.57	8.429%	$222.8975	$222.90	$222.90	$222.90
Purchase #2	$175.39	11.816%	$196.1141	$196.11	$196.10	$196.10
Purchase #3	$63.60	12.470%	$71.5309	$71.53	$71.55	$71.50
Purchase #4	$224.43	6.697%	$239.4601	$239.46	$239.45	$239.50
Purchase #5	$31.66	10.423%	$34.9599	$34.96	$34.95	$35.00
Purchase #6	$16.97	11.692%	$18.9541	$18.95	$18.95	$19.00
Purchase #7	$244.28	5.763%	$258.3579	$258.36	$258.35	$258.40
7 purchase totals =	$961.90		$1,042.2745	$1,042.27	$1,042.25	$1,042.40