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	$205.88	8.160%	$222.6798	$222.68	$222.70	$222.70
Purchase #2	$19.50	11.810%	$21.803	$21.80	$21.80	$21.80
Purchase #3	$86.68	3.402%	$89.6289	$89.63	$89.65	$89.60
Purchase #4	$145.76	13.541%	$165.4974	$165.50	$165.50	$165.50
Purchase #5	$125.96	9.483%	$137.9048	$137.90	$137.90	$137.90
Purchase #6	$181.98	9.833%	$199.8741	$199.87	$199.85	$199.90
Purchase #7	$93.63	6.584%	$99.7946	$99.79	$99.80	$99.80
7 purchase totals =	$859.39		$937.1826	$937.17	$937.20	$937.20