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	$137.95	7.170%	$147.841	$147.84	$147.85	$147.80
Purchase #2	$192.99	5.485%	$203.5755	$203.58	$203.60	$203.60
Purchase #3	$185.95	5.728%	$196.6012	$196.60	$196.60	$196.60
Purchase #4	$198.42	12.181%	$222.5895	$222.59	$222.60	$222.60
Purchase #5	$242.81	10.464%	$268.2176	$268.22	$268.20	$268.20
Purchase #6	$164.46	6.509%	$175.1647	$175.16	$175.15	$175.20
Purchase #7	$228.83	13.442%	$259.5893	$259.59	$259.60	$259.60
7 purchase totals =	$1,351.41		$1,473.5788	$1,473.58	$1,473.60	$1,473.60