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	$14.72	4.279%	$15.3499	$15.35	$15.35	$15.30
Purchase #2	$250.96	5.730%	$265.34	$265.34	$265.35	$265.30
Purchase #3	$174.44	12.555%	$196.3409	$196.34	$196.35	$196.30
Purchase #4	$233.98	3.251%	$241.5867	$241.59	$241.60	$241.60
Purchase #5	$196.71	10.682%	$217.7226	$217.72	$217.70	$217.70
Purchase #6	$73.64	13.350%	$83.4709	$83.47	$83.45	$83.50
Purchase #7	$224.54	13.757%	$255.43	$255.43	$255.45	$255.40
7 purchase totals =	$1,168.99		$1,275.2410	$1,275.24	$1,275.25	$1,275.10