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	$146.61	4.397%	$153.0564	$153.06	$153.05	$153.10
Purchase #2	$179.98	5.479%	$189.8411	$189.84	$189.85	$189.80
Purchase #3	$31.57	7.123%	$33.8187	$33.82	$33.80	$33.80
Purchase #4	$131.26	6.606%	$139.931	$139.93	$139.95	$139.90
Purchase #5	$239.60	6.855%	$256.0246	$256.02	$256.00	$256.00
Purchase #6	$6.63	11.526%	$7.3942	$7.39	$7.40	$7.40
Purchase #7	$163.85	8.801%	$178.2704	$178.27	$178.25	$178.30
7 purchase totals =	$899.50		$958.3364	$958.33	$958.30	$958.30