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	$144.67	13.620%	$164.3741	$164.37	$164.35	$164.40
Purchase #2	$137.48	4.123%	$143.1483	$143.15	$143.15	$143.10
Purchase #3	$23.83	13.137%	$26.9605	$26.96	$26.95	$27.00
Purchase #4	$133.35	6.787%	$142.4005	$142.40	$142.40	$142.40
Purchase #5	$222.79	7.232%	$238.9022	$238.90	$238.90	$238.90
Purchase #6	$68.51	12.114%	$76.8093	$76.81	$76.80	$76.80
Purchase #7	$246.62	4.739%	$258.3073	$258.31	$258.30	$258.30
7 purchase totals =	$977.25		$1,050.9022	$1,050.90	$1,050.85	$1,050.90