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	$140.59	11.595%	$156.8914	$156.89	$156.90	$156.90
Purchase #2	$202.67	11.154%	$225.2758	$225.28	$225.30	$225.30
Purchase #3	$56.68	9.168%	$61.8764	$61.88	$61.90	$61.90
Purchase #4	$53.57	12.578%	$60.308	$60.31	$60.30	$60.30
Purchase #5	$125.79	4.796%	$131.8229	$131.82	$131.80	$131.80
Purchase #6	$61.72	8.155%	$66.7533	$66.75	$66.75	$66.80
Purchase #7	$231.93	4.124%	$241.4948	$241.49	$241.50	$241.50
7 purchase totals =	$872.95		$944.4226	$944.42	$944.45	$944.50