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	$189.84	5.792%	$200.8355	$200.84	$200.85	$200.80
Purchase #2	$234.70	8.768%	$255.2785	$255.28	$255.30	$255.30
Purchase #3	$190.78	3.189%	$196.864	$196.86	$196.85	$196.90
Purchase #4	$58.63	8.788%	$63.7824	$63.78	$63.80	$63.80
Purchase #5	$39.33	12.215%	$44.1342	$44.13	$44.15	$44.10
Purchase #6	$135.38	12.779%	$152.6802	$152.68	$152.70	$152.70
Purchase #7	$228.89	7.147%	$245.2488	$245.25	$245.25	$245.20
7 purchase totals =	$1,077.55		$1,158.8236	$1,158.82	$1,158.90	$1,158.80