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	$109.28	8.684%	$118.7699	$118.77	$118.75	$118.80
Purchase #2	$41.95	8.515%	$45.522	$45.52	$45.50	$45.50
Purchase #3	$32.68	7.422%	$35.1055	$35.11	$35.10	$35.10
Purchase #4	$213.54	8.179%	$231.0054	$231.01	$231.00	$231.00
Purchase #5	$70.35	4.665%	$73.6318	$73.63	$73.65	$73.60
Purchase #6	$90.96	5.864%	$96.2939	$96.29	$96.30	$96.30
Purchase #7	$169.63	9.523%	$185.7839	$185.78	$185.80	$185.80
7 purchase totals =	$728.39		$786.1124	$786.11	$786.10	$786.10