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	$63.27	7.833%	$68.2259	$68.23	$68.25	$68.20
Purchase #2	$124.47	3.247%	$128.5115	$128.51	$128.50	$128.50
Purchase #3	$153.54	7.385%	$164.8789	$164.88	$164.90	$164.90
Purchase #4	$183.89	13.542%	$208.7924	$208.79	$208.80	$208.80
Purchase #5	$172.35	12.873%	$194.5366	$194.54	$194.55	$194.50
Purchase #6	$154.47	12.803%	$174.2468	$174.25	$174.25	$174.20
Purchase #7	$166.61	7.771%	$179.5573	$179.56	$179.55	$179.60
7 purchase totals =	$1,018.60		$1,118.7494	$1,118.76	$1,118.80	$1,118.70