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	$198.73	6.585%	$211.8164	$211.82	$211.80	$211.80
Purchase #2	$218.99	9.855%	$240.5715	$240.57	$240.55	$240.60
Purchase #3	$40.88	7.442%	$43.9223	$43.92	$43.90	$43.90
Purchase #4	$89.45	3.425%	$92.5137	$92.51	$92.50	$92.50
Purchase #5	$240.75	11.228%	$267.7814	$267.78	$267.80	$267.80
Purchase #6	$18.88	8.608%	$20.5052	$20.51	$20.50	$20.50
Purchase #7	$128.25	7.255%	$137.5545	$137.55	$137.55	$137.60
7 purchase totals =	$935.93		$1,014.6650	$1,014.66	$1,014.60	$1,014.70