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	$174.55	9.208%	$190.6226	$190.62	$190.60	$190.60
Purchase #2	$229.74	10.488%	$253.8351	$253.84	$253.85	$253.80
Purchase #3	$140.93	7.182%	$151.0516	$151.05	$151.05	$151.10
Purchase #4	$185.77	9.254%	$202.9612	$202.96	$202.95	$203.00
Purchase #5	$69.81	4.377%	$72.8656	$72.87	$72.85	$72.90
Purchase #6	$36.93	10.651%	$40.8634	$40.86	$40.85	$40.90
Purchase #7	$19.99	3.651%	$20.7198	$20.72	$20.70	$20.70
7 purchase totals =	$857.72		$932.9193	$932.92	$932.85	$933.00