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	$41.49	10.206%	$45.7245	$45.72	$45.70	$45.70
Purchase #2	$213.55	12.531%	$240.31	$240.31	$240.30	$240.30
Purchase #3	$180.47	13.638%	$205.0825	$205.08	$205.10	$205.10
Purchase #4	$245.76	8.464%	$266.5611	$266.56	$266.55	$266.60
Purchase #5	$157.99	13.759%	$179.7278	$179.73	$179.75	$179.70
Purchase #6	$32.41	4.436%	$33.8477	$33.85	$33.85	$33.80
Purchase #7	$38.92	4.302%	$40.5943	$40.59	$40.60	$40.60
7 purchase totals =	$910.59		$1,011.8479	$1,011.84	$1,011.85	$1,011.80