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	$87.73	10.727%	$97.1408	$97.14	$97.15	$97.10
Purchase #2	$189.77	6.509%	$202.1221	$202.12	$202.10	$202.10
Purchase #3	$194.48	8.429%	$210.8727	$210.87	$210.85	$210.90
Purchase #4	$36.84	13.155%	$41.6863	$41.69	$41.70	$41.70
Purchase #5	$80.89	10.742%	$89.5792	$89.58	$89.60	$89.60
Purchase #6	$182.34	7.279%	$195.6125	$195.61	$195.60	$195.60
Purchase #7	$82.52	8.141%	$89.238	$89.24	$89.25	$89.20
7 purchase totals =	$854.57		$926.2516	$926.25	$926.25	$926.20