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	$35.32	9.769%	$38.7704	$38.77	$38.75	$38.80
Purchase #2	$78.66	13.143%	$88.9983	$89.00	$89.00	$89.00
Purchase #3	$237.57	11.407%	$264.6696	$264.67	$264.65	$264.70
Purchase #4	$238.63	7.609%	$256.7874	$256.79	$256.80	$256.80
Purchase #5	$88.78	8.241%	$96.0964	$96.10	$96.10	$96.10
Purchase #6	$97.72	5.836%	$103.4229	$103.42	$103.40	$103.40
Purchase #7	$36.73	5.420%	$38.7208	$38.72	$38.70	$38.70
7 purchase totals =	$813.41		$887.4658	$887.47	$887.40	$887.50