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	$31.32	6.865%	$33.4701	$33.47	$33.45	$33.50
Purchase #2	$181.98	10.183%	$200.511	$200.51	$200.50	$200.50
Purchase #3	$138.38	3.855%	$143.7145	$143.71	$143.70	$143.70
Purchase #4	$5.95	7.650%	$6.4052	$6.41	$6.40	$6.40
Purchase #5	$158.38	10.368%	$174.8008	$174.80	$174.80	$174.80
Purchase #6	$210.25	6.344%	$223.5883	$223.59	$223.60	$223.60
Purchase #7	$236.51	9.512%	$259.0068	$259.01	$259.00	$259.00
7 purchase totals =	$962.77		$1,041.4967	$1,041.50	$1,041.45	$1,041.50