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	$63.95	13.792%	$72.77	$72.77	$72.75	$72.80
Purchase #2	$228.71	4.514%	$239.034	$239.03	$239.05	$239.00
Purchase #3	$63.85	13.142%	$72.2412	$72.24	$72.25	$72.20
Purchase #4	$187.71	12.548%	$211.2639	$211.26	$211.25	$211.30
Purchase #5	$81.49	6.127%	$86.4829	$86.48	$86.50	$86.50
Purchase #6	$95.34	3.758%	$98.9229	$98.92	$98.90	$98.90
Purchase #7	$39.90	3.675%	$41.3663	$41.37	$41.35	$41.40
7 purchase totals =	$760.95		$822.0812	$822.07	$822.05	$822.10