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	$37.51	3.680%	$38.8904	$38.89	$38.90	$38.90
Purchase #2	$213.60	3.585%	$221.2576	$221.26	$221.25	$221.30
Purchase #3	$109.80	11.633%	$122.573	$122.57	$122.55	$122.60
Purchase #4	$205.25	11.238%	$228.316	$228.32	$228.30	$228.30
Purchase #5	$133.85	9.689%	$146.8187	$146.82	$146.80	$146.80
Purchase #6	$174.62	3.686%	$181.0565	$181.06	$181.05	$181.10
Purchase #7	$87.89	13.192%	$99.4844	$99.48	$99.50	$99.50
7 purchase totals =	$962.52		$1,038.3966	$1,038.40	$1,038.35	$1,038.50