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	$53.64	3.667%	$55.607	$55.61	$55.60	$55.60
Purchase #2	$72.93	8.181%	$78.8964	$78.90	$78.90	$78.90
Purchase #3	$7.27	4.532%	$7.5995	$7.60	$7.60	$7.60
Purchase #4	$170.91	13.267%	$193.5846	$193.58	$193.60	$193.60
Purchase #5	$128.63	10.870%	$142.6121	$142.61	$142.60	$142.60
Purchase #6	$158.86	5.858%	$168.166	$168.17	$168.15	$168.20
Purchase #7	$169.80	4.813%	$177.9725	$177.97	$177.95	$178.00
7 purchase totals =	$762.04		$824.4381	$824.44	$824.40	$824.50