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	$93.25	10.260%	$102.8175	$102.82	$102.80	$102.80
Purchase #2	$27.74	6.629%	$29.5789	$29.58	$29.60	$29.60
Purchase #3	$231.40	4.835%	$242.5882	$242.59	$242.60	$242.60
Purchase #4	$78.55	12.511%	$88.3774	$88.38	$88.40	$88.40
Purchase #5	$19.59	4.393%	$20.4506	$20.45	$20.45	$20.50
Purchase #6	$33.64	5.194%	$35.3873	$35.39	$35.40	$35.40
Purchase #7	$111.69	12.151%	$125.2615	$125.26	$125.25	$125.30
7 purchase totals =	$595.86		$644.4614	$644.47	$644.50	$644.60