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	$92.82	6.164%	$98.5414	$98.54	$98.55	$98.50
Purchase #2	$94.69	10.326%	$104.4677	$104.47	$104.45	$104.50
Purchase #3	$40.64	11.409%	$45.2766	$45.28	$45.30	$45.30
Purchase #4	$201.91	3.394%	$208.7628	$208.76	$208.75	$208.80
Purchase #5	$217.72	11.378%	$242.4922	$242.49	$242.50	$242.50
Purchase #6	$104.78	7.746%	$112.8963	$112.90	$112.90	$112.90
Purchase #7	$217.92	11.282%	$242.5057	$242.51	$242.50	$242.50
7 purchase totals =	$970.48		$1,054.9427	$1,054.95	$1,054.95	$1,055.00