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	$165.92	6.605%	$176.879	$176.88	$176.90	$176.90
Purchase #2	$166.47	5.424%	$175.4993	$175.50	$175.50	$175.50
Purchase #3	$149.66	4.859%	$156.932	$156.93	$156.95	$156.90
Purchase #4	$154.54	7.518%	$166.1583	$166.16	$166.15	$166.20
Purchase #5	$36.67	7.829%	$39.5409	$39.54	$39.55	$39.50
Purchase #6	$137.38	13.127%	$155.4139	$155.41	$155.40	$155.40
Purchase #7	$156.54	10.194%	$172.4977	$172.50	$172.50	$172.50
7 purchase totals =	$967.18		$1,042.9211	$1,042.92	$1,042.95	$1,042.90