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	$112.56	13.120%	$127.3279	$127.33	$127.35	$127.30
Purchase #2	$214.81	13.618%	$244.0628	$244.06	$244.05	$244.10
Purchase #3	$141.75	11.409%	$157.9223	$157.92	$157.90	$157.90
Purchase #4	$38.50	4.743%	$40.3261	$40.33	$40.35	$40.30
Purchase #5	$86.72	13.672%	$98.5764	$98.58	$98.60	$98.60
Purchase #6	$47.85	8.553%	$51.9426	$51.94	$51.95	$51.90
Purchase #7	$180.29	13.252%	$204.182	$204.18	$204.20	$204.20
7 purchase totals =	$822.48		$924.3401	$924.34	$924.40	$924.30