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	$131.89	7.392%	$141.6393	$141.64	$141.65	$141.60
Purchase #2	$104.83	12.325%	$117.7503	$117.75	$117.75	$117.80
Purchase #3	$234.48	5.466%	$247.2967	$247.30	$247.30	$247.30
Purchase #4	$245.43	4.418%	$256.2731	$256.27	$256.25	$256.30
Purchase #5	$33.97	13.291%	$38.485	$38.49	$38.50	$38.50
Purchase #6	$11.82	10.256%	$13.0323	$13.03	$13.05	$13.00
Purchase #7	$231.83	5.424%	$244.4045	$244.40	$244.40	$244.40
7 purchase totals =	$994.25		$1,058.8812	$1,058.88	$1,058.90	$1,058.90