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	$85.84	10.530%	$94.879	$94.88	$94.90	$94.90
Purchase #2	$97.42	7.693%	$104.9145	$104.91	$104.90	$104.90
Purchase #3	$82.53	4.555%	$86.2892	$86.29	$86.30	$86.30
Purchase #4	$19.84	5.492%	$20.9296	$20.93	$20.95	$20.90
Purchase #5	$12.66	13.345%	$14.3495	$14.35	$14.35	$14.30
Purchase #6	$117.36	13.600%	$133.321	$133.32	$133.30	$133.30
Purchase #7	$37.83	11.297%	$42.1037	$42.10	$42.10	$42.10
7 purchase totals =	$453.48		$496.7865	$496.78	$496.80	$496.70