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	$98.67	12.750%	$111.2504	$111.25	$111.25	$111.30
Purchase #2	$214.92	12.454%	$241.6861	$241.69	$241.70	$241.70
Purchase #3	$45.78	4.176%	$47.6918	$47.69	$47.70	$47.70
Purchase #4	$189.31	3.620%	$196.163	$196.16	$196.15	$196.20
Purchase #5	$243.52	12.848%	$274.8074	$274.81	$274.80	$274.80
Purchase #6	$216.36	11.708%	$241.6914	$241.69	$241.70	$241.70
Purchase #7	$188.75	4.257%	$196.7851	$196.79	$196.80	$196.80
7 purchase totals =	$1,197.31		$1,310.0752	$1,310.08	$1,310.10	$1,310.20