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	$60.86	5.320%	$64.0978	$64.10	$64.10	$64.10
Purchase #2	$202.61	6.526%	$215.8323	$215.83	$215.85	$215.80
Purchase #3	$193.32	3.186%	$199.4792	$199.48	$199.50	$199.50
Purchase #4	$219.86	13.401%	$249.3234	$249.32	$249.30	$249.30
Purchase #5	$75.49	10.775%	$83.624	$83.62	$83.60	$83.60
Purchase #6	$57.52	3.447%	$59.5027	$59.50	$59.50	$59.50
Purchase #7	$212.72	13.208%	$240.8161	$240.82	$240.80	$240.80
7 purchase totals =	$1,022.38		$1,112.6755	$1,112.67	$1,112.65	$1,112.60