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	$12.38	5.125%	$13.0145	$13.01	$13.00	$13.00
Purchase #2	$176.71	6.700%	$188.5496	$188.55	$188.55	$188.50
Purchase #3	$198.33	13.534%	$225.172	$225.17	$225.15	$225.20
Purchase #4	$124.34	6.831%	$132.8337	$132.83	$132.85	$132.80
Purchase #5	$212.80	13.689%	$241.9302	$241.93	$241.95	$241.90
Purchase #6	$174.95	6.358%	$186.0733	$186.07	$186.05	$186.10
Purchase #7	$52.90	12.270%	$59.3908	$59.39	$59.40	$59.40
7 purchase totals =	$952.41		$1,046.9641	$1,046.95	$1,046.95	$1,046.90