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	$72.38	8.564%	$78.5786	$78.58	$78.60	$78.60
Purchase #2	$113.64	10.195%	$125.2256	$125.23	$125.25	$125.20
Purchase #3	$137.40	3.700%	$142.4838	$142.48	$142.50	$142.50
Purchase #4	$182.53	4.271%	$190.3259	$190.33	$190.35	$190.30
Purchase #5	$171.83	3.725%	$178.2307	$178.23	$178.25	$178.20
Purchase #6	$104.67	10.593%	$115.7577	$115.76	$115.75	$115.80
Purchase #7	$195.86	4.561%	$204.7932	$204.79	$204.80	$204.80
7 purchase totals =	$978.31		$1,035.3955	$1,035.40	$1,035.50	$1,035.40