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	$191.71	6.384%	$203.9488	$203.95	$203.95	$203.90
Purchase #2	$178.31	10.441%	$196.9273	$196.93	$196.95	$196.90
Purchase #3	$124.66	10.349%	$137.5611	$137.56	$137.55	$137.60
Purchase #4	$111.89	4.469%	$116.8904	$116.89	$116.90	$116.90
Purchase #5	$208.26	5.511%	$219.7372	$219.74	$219.75	$219.70
Purchase #6	$123.49	12.857%	$139.3671	$139.37	$139.35	$139.40
Purchase #7	$202.89	9.361%	$221.8825	$221.88	$221.90	$221.90
7 purchase totals =	$1,141.21		$1,236.3144	$1,236.32	$1,236.35	$1,236.30