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	$187.67	4.741%	$196.5674	$196.57	$196.55	$196.60
Purchase #2	$18.97	7.521%	$20.3967	$20.40	$20.40	$20.40
Purchase #3	$157.61	4.366%	$164.4913	$164.49	$164.50	$164.50
Purchase #4	$33.65	12.362%	$37.8098	$37.81	$37.80	$37.80
Purchase #5	$6.85	10.754%	$7.5866	$7.59	$7.60	$7.60
Purchase #6	$185.26	4.262%	$193.1558	$193.16	$193.15	$193.20
Purchase #7	$73.82	6.718%	$78.7792	$78.78	$78.80	$78.80
7 purchase totals =	$663.83		$698.7868	$698.80	$698.80	$698.90