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	$102.38	5.823%	$108.3416	$108.34	$108.35	$108.30
Purchase #2	$121.89	8.555%	$132.3177	$132.32	$132.30	$132.30
Purchase #3	$34.78	3.211%	$35.8968	$35.90	$35.90	$35.90
Purchase #4	$179.76	9.107%	$196.1307	$196.13	$196.15	$196.10
Purchase #5	$67.93	5.341%	$71.5581	$71.56	$71.55	$71.60
Purchase #6	$82.71	4.446%	$86.3873	$86.39	$86.40	$86.40
Purchase #7	$187.62	9.559%	$205.5546	$205.55	$205.55	$205.60
7 purchase totals =	$777.07		$836.1868	$836.19	$836.20	$836.20