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	$218.67	3.762%	$226.8964	$226.90	$226.90	$226.90
Purchase #2	$73.45	11.631%	$81.993	$81.99	$82.00	$82.00
Purchase #3	$173.50	13.304%	$196.5824	$196.58	$196.60	$196.60
Purchase #4	$163.84	10.680%	$181.3381	$181.34	$181.35	$181.30
Purchase #5	$186.65	7.490%	$200.6301	$200.63	$200.65	$200.60
Purchase #6	$131.67	13.443%	$149.3704	$149.37	$149.35	$149.40
Purchase #7	$37.86	12.162%	$42.4645	$42.46	$42.45	$42.50
7 purchase totals =	$985.64		$1,079.2749	$1,079.27	$1,079.30	$1,079.30