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	$53.66	4.287%	$55.9604	$55.96	$55.95	$56.00
Purchase #2	$131.51	5.717%	$139.0284	$139.03	$139.05	$139.00
Purchase #3	$62.98	5.265%	$66.2959	$66.30	$66.30	$66.30
Purchase #4	$234.91	3.802%	$243.8413	$243.84	$243.85	$243.80
Purchase #5	$156.52	8.490%	$169.8085	$169.81	$169.80	$169.80
Purchase #6	$12.53	10.284%	$13.8186	$13.82	$13.80	$13.80
Purchase #7	$189.78	4.573%	$198.4586	$198.46	$198.45	$198.50
7 purchase totals =	$841.89		$887.2117	$887.22	$887.20	$887.20