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	$213.75	4.114%	$222.5437	$222.54	$222.55	$222.50
Purchase #2	$27.77	9.765%	$30.4817	$30.48	$30.50	$30.50
Purchase #3	$168.83	8.545%	$183.2565	$183.26	$183.25	$183.30
Purchase #4	$161.59	11.685%	$180.4718	$180.47	$180.45	$180.50
Purchase #5	$230.32	6.178%	$244.5492	$244.55	$244.55	$244.50
Purchase #6	$71.53	9.138%	$78.0664	$78.07	$78.05	$78.10
Purchase #7	$92.76	10.383%	$102.3913	$102.39	$102.40	$102.40
7 purchase totals =	$966.55		$1,041.7606	$1,041.76	$1,041.75	$1,041.80