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	$238.68	9.312%	$260.9059	$260.91	$260.90	$260.90
Purchase #2	$84.83	3.352%	$87.6735	$87.67	$87.65	$87.70
Purchase #3	$148.82	13.372%	$168.7202	$168.72	$168.70	$168.70
Purchase #4	$208.52	3.471%	$215.7577	$215.76	$215.75	$215.80
Purchase #5	$208.91	3.352%	$215.9127	$215.91	$215.90	$215.90
Purchase #6	$74.85	5.297%	$78.8148	$78.81	$78.80	$78.80
Purchase #7	$83.46	6.809%	$89.1428	$89.14	$89.15	$89.10
7 purchase totals =	$1,048.07		$1,116.9276	$1,116.92	$1,116.85	$1,116.90