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	$232.50	3.462%	$240.5492	$240.55	$240.55	$240.50
Purchase #2	$195.61	9.261%	$213.7254	$213.73	$213.75	$213.70
Purchase #3	$170.71	11.408%	$190.1846	$190.18	$190.20	$190.20
Purchase #4	$94.76	5.831%	$100.2855	$100.29	$100.30	$100.30
Purchase #5	$67.97	6.405%	$72.3235	$72.32	$72.30	$72.30
Purchase #6	$74.90	9.406%	$81.9451	$81.95	$81.95	$81.90
Purchase #7	$222.85	6.801%	$238.006	$238.01	$238.00	$238.00
7 purchase totals =	$1,059.30		$1,137.0193	$1,137.03	$1,137.05	$1,136.90