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	$82.40	8.601%	$89.4872	$89.49	$89.50	$89.50
Purchase #2	$133.34	7.524%	$143.3725	$143.37	$143.35	$143.40
Purchase #3	$134.50	11.695%	$150.2298	$150.23	$150.25	$150.20
Purchase #4	$190.50	10.370%	$210.2549	$210.25	$210.25	$210.30
Purchase #5	$86.61	7.324%	$92.9533	$92.95	$92.95	$93.00
Purchase #6	$85.55	6.745%	$91.3203	$91.32	$91.30	$91.30
Purchase #7	$212.95	7.311%	$228.5188	$228.52	$228.50	$228.50
7 purchase totals =	$925.85		$1,006.1368	$1,006.13	$1,006.10	$1,006.20