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	$58.63	4.555%	$61.3006	$61.30	$61.30	$61.30
Purchase #2	$51.39	12.699%	$57.916	$57.92	$57.90	$57.90
Purchase #3	$75.86	10.171%	$83.5757	$83.58	$83.60	$83.60
Purchase #4	$84.40	9.591%	$92.4948	$92.49	$92.50	$92.50
Purchase #5	$247.40	12.774%	$279.0029	$279.00	$279.00	$279.00
Purchase #6	$244.61	8.567%	$265.5657	$265.57	$265.55	$265.60
Purchase #7	$248.71	4.193%	$259.1384	$259.14	$259.15	$259.10
7 purchase totals =	$1,011.00		$1,098.9941	$1,099.00	$1,099.00	$1,099.00