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	$191.80	13.443%	$217.5837	$217.58	$217.60	$217.60
Purchase #2	$246.59	6.222%	$261.9328	$261.93	$261.95	$261.90
Purchase #3	$43.34	12.740%	$48.8615	$48.86	$48.85	$48.90
Purchase #4	$135.48	5.213%	$142.5426	$142.54	$142.55	$142.50
Purchase #5	$161.84	7.194%	$173.4828	$173.48	$173.50	$173.50
Purchase #6	$102.84	13.266%	$116.4828	$116.48	$116.50	$116.50
Purchase #7	$243.65	4.379%	$254.3194	$254.32	$254.30	$254.30
7 purchase totals =	$1,125.54		$1,215.2056	$1,215.19	$1,215.25	$1,215.20