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	$56.87	7.356%	$61.0534	$61.05	$61.05	$61.10
Purchase #2	$222.98	4.486%	$232.9829	$232.98	$233.00	$233.00
Purchase #3	$48.79	13.278%	$55.2683	$55.27	$55.25	$55.30
Purchase #4	$126.94	8.543%	$137.7845	$137.78	$137.80	$137.80
Purchase #5	$233.33	9.706%	$255.977	$255.98	$256.00	$256.00
Purchase #6	$164.27	11.740%	$183.5553	$183.56	$183.55	$183.60
Purchase #7	$189.86	13.324%	$215.1569	$215.16	$215.15	$215.20
7 purchase totals =	$1,043.04		$1,141.7783	$1,141.78	$1,141.80	$1,142.00