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	$207.73	9.809%	$228.1062	$228.11	$228.10	$228.10
Purchase #2	$19.60	12.287%	$22.0083	$22.01	$22.00	$22.00
Purchase #3	$13.45	10.119%	$14.811	$14.81	$14.80	$14.80
Purchase #4	$78.35	4.737%	$82.0614	$82.06	$82.05	$82.10
Purchase #5	$115.28	10.299%	$127.1527	$127.15	$127.15	$127.20
Purchase #6	$78.58	4.619%	$82.2096	$82.21	$82.20	$82.20
Purchase #7	$132.32	9.287%	$144.6086	$144.61	$144.60	$144.60
7 purchase totals =	$645.31		$700.9578	$700.96	$700.90	$701.00