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	$227.82	9.187%	$248.7498	$248.75	$248.75	$248.70
Purchase #2	$33.97	8.807%	$36.9617	$36.96	$36.95	$37.00
Purchase #3	$131.85	7.298%	$141.4724	$141.47	$141.45	$141.50
Purchase #4	$175.66	3.633%	$182.0417	$182.04	$182.05	$182.00
Purchase #5	$231.79	4.308%	$241.7755	$241.78	$241.80	$241.80
Purchase #6	$100.83	10.326%	$111.2417	$111.24	$111.25	$111.20
Purchase #7	$86.37	6.445%	$91.9365	$91.94	$91.95	$91.90
7 purchase totals =	$988.29		$1,054.1793	$1,054.18	$1,054.20	$1,054.10