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	$238.39	10.803%	$264.1433	$264.14	$264.15	$264.10
Purchase #2	$242.31	4.533%	$253.2939	$253.29	$253.30	$253.30
Purchase #3	$45.26	3.396%	$46.797	$46.80	$46.80	$46.80
Purchase #4	$202.59	5.617%	$213.9695	$213.97	$213.95	$214.00
Purchase #5	$83.38	7.355%	$89.5126	$89.51	$89.50	$89.50
Purchase #6	$230.47	5.661%	$243.5169	$243.52	$243.50	$243.50
Purchase #7	$217.76	7.108%	$233.2384	$233.24	$233.25	$233.20
7 purchase totals =	$1,260.16		$1,344.4716	$1,344.47	$1,344.45	$1,344.40