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	$207.70	6.356%	$220.9014	$220.90	$220.90	$220.90
Purchase #2	$51.99	3.298%	$53.7046	$53.70	$53.70	$53.70
Purchase #3	$94.56	6.261%	$100.4804	$100.48	$100.50	$100.50
Purchase #4	$191.80	11.355%	$213.5789	$213.58	$213.60	$213.60
Purchase #5	$93.56	7.698%	$100.7622	$100.76	$100.75	$100.80
Purchase #6	$131.77	13.547%	$149.6209	$149.62	$149.60	$149.60
Purchase #7	$240.77	13.575%	$273.4545	$273.45	$273.45	$273.50
7 purchase totals =	$1,012.15		$1,112.5029	$1,112.49	$1,112.50	$1,112.60