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	$195.60	4.765%	$204.9203	$204.92	$204.90	$204.90
Purchase #2	$77.92	5.408%	$82.1339	$82.13	$82.15	$82.10
Purchase #3	$177.99	12.762%	$200.7051	$200.71	$200.70	$200.70
Purchase #4	$128.43	12.805%	$144.8755	$144.88	$144.90	$144.90
Purchase #5	$122.71	12.321%	$137.8291	$137.83	$137.85	$137.80
Purchase #6	$121.87	7.728%	$131.2881	$131.29	$131.30	$131.30
Purchase #7	$35.39	7.384%	$38.0032	$38.00	$38.00	$38.00
7 purchase totals =	$859.91		$939.7552	$939.76	$939.80	$939.70