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	$176.40	10.481%	$194.8885	$194.89	$194.90	$194.90
Purchase #2	$126.82	6.435%	$134.9809	$134.98	$135.00	$135.00
Purchase #3	$233.56	9.591%	$255.9607	$255.96	$255.95	$256.00
Purchase #4	$81.71	13.254%	$92.5398	$92.54	$92.55	$92.50
Purchase #5	$140.60	11.223%	$156.3795	$156.38	$156.40	$156.40
Purchase #6	$141.95	12.405%	$159.5589	$159.56	$159.55	$159.60
Purchase #7	$93.44	12.703%	$105.3097	$105.31	$105.30	$105.30
7 purchase totals =	$994.48		$1,099.6180	$1,099.62	$1,099.65	$1,099.70