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	$143.88	4.397%	$150.2064	$150.21	$150.20	$150.20
Purchase #2	$188.60	5.720%	$199.3879	$199.39	$199.40	$199.40
Purchase #3	$19.52	8.705%	$21.2192	$21.22	$21.20	$21.20
Purchase #4	$154.75	12.749%	$174.4791	$174.48	$174.50	$174.50
Purchase #5	$89.51	8.248%	$96.8928	$96.89	$96.90	$96.90
Purchase #6	$68.87	5.684%	$72.7846	$72.78	$72.80	$72.80
Purchase #7	$59.43	4.155%	$61.8993	$61.90	$61.90	$61.90
7 purchase totals =	$724.56		$776.8693	$776.87	$776.90	$776.90