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	$231.55	4.241%	$241.37	$241.37	$241.35	$241.40
Purchase #2	$78.74	4.739%	$82.4715	$82.47	$82.45	$82.50
Purchase #3	$200.97	5.857%	$212.7408	$212.74	$212.75	$212.70
Purchase #4	$202.51	10.492%	$223.7573	$223.76	$223.75	$223.80
Purchase #5	$179.76	5.861%	$190.2957	$190.30	$190.30	$190.30
Purchase #6	$101.65	3.120%	$104.8215	$104.82	$104.80	$104.80
Purchase #7	$116.75	7.799%	$125.8553	$125.86	$125.85	$125.90
7 purchase totals =	$1,111.93		$1,181.3121	$1,181.32	$1,181.25	$1,181.40