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	$55.68	11.221%	$61.9279	$61.93	$61.95	$61.90
Purchase #2	$152.54	7.786%	$164.4168	$164.42	$164.40	$164.40
Purchase #3	$139.43	10.519%	$154.0966	$154.10	$154.10	$154.10
Purchase #4	$84.80	10.234%	$93.4784	$93.48	$93.50	$93.50
Purchase #5	$59.40	5.722%	$62.7989	$62.80	$62.80	$62.80
Purchase #6	$94.38	3.689%	$97.8617	$97.86	$97.85	$97.90
Purchase #7	$94.54	3.554%	$97.9	$97.90	$97.90	$97.90
7 purchase totals =	$680.77		$732.4803	$732.49	$732.50	$732.50