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	$140.61	8.422%	$152.4522	$152.45	$152.45	$152.50
Purchase #2	$179.72	6.769%	$191.8852	$191.89	$191.90	$191.90
Purchase #3	$182.89	8.264%	$198.004	$198.00	$198.00	$198.00
Purchase #4	$149.66	3.447%	$154.8188	$154.82	$154.80	$154.80
Purchase #5	$212.96	6.337%	$226.4553	$226.46	$226.45	$226.50
Purchase #6	$200.53	6.358%	$213.2797	$213.28	$213.30	$213.30
Purchase #7	$70.65	10.727%	$78.2286	$78.23	$78.25	$78.20
7 purchase totals =	$1,137.02		$1,215.1238	$1,215.13	$1,215.15	$1,215.20