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	$142.25	7.331%	$152.6783	$152.68	$152.70	$152.70
Purchase #2	$233.57	10.258%	$257.5296	$257.53	$257.55	$257.50
Purchase #3	$158.51	8.808%	$172.4716	$172.47	$172.45	$172.50
Purchase #4	$52.90	8.807%	$57.5589	$57.56	$57.55	$57.60
Purchase #5	$207.48	6.701%	$221.3832	$221.38	$221.40	$221.40
Purchase #6	$124.79	10.173%	$137.4849	$137.48	$137.50	$137.50
Purchase #7	$9.88	8.638%	$10.7334	$10.73	$10.75	$10.70
7 purchase totals =	$929.38		$1,009.8399	$1,009.83	$1,009.90	$1,009.90