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	$92.88	10.529%	$102.6593	$102.66	$102.65	$102.70
Purchase #2	$17.43	8.532%	$18.9171	$18.92	$18.90	$18.90
Purchase #3	$196.54	11.732%	$219.5981	$219.60	$219.60	$219.60
Purchase #4	$106.72	6.449%	$113.6024	$113.60	$113.60	$113.60
Purchase #5	$106.96	9.102%	$116.6955	$116.70	$116.70	$116.70
Purchase #6	$154.42	11.847%	$172.7141	$172.71	$172.70	$172.70
Purchase #7	$238.42	11.244%	$265.2279	$265.23	$265.25	$265.20
7 purchase totals =	$913.37		$1,009.4144	$1,009.42	$1,009.40	$1,009.40