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	$76.59	6.819%	$81.8127	$81.81	$81.80	$81.80
Purchase #2	$196.39	10.641%	$217.2879	$217.29	$217.30	$217.30
Purchase #3	$106.91	10.856%	$118.5161	$118.52	$118.50	$118.50
Purchase #4	$91.43	8.215%	$98.941	$98.94	$98.95	$98.90
Purchase #5	$166.56	11.511%	$185.7327	$185.73	$185.75	$185.70
Purchase #6	$31.78	11.564%	$35.455	$35.46	$35.45	$35.50
Purchase #7	$28.63	12.345%	$32.1644	$32.16	$32.15	$32.20
7 purchase totals =	$698.29		$769.9098	$769.91	$769.90	$769.90