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	$57.40	10.260%	$63.2892	$63.29	$63.30	$63.30
Purchase #2	$219.95	9.321%	$240.4515	$240.45	$240.45	$240.50
Purchase #3	$219.79	6.472%	$234.0148	$234.01	$234.00	$234.00
Purchase #4	$42.45	3.570%	$43.9655	$43.97	$43.95	$44.00
Purchase #5	$240.29	10.456%	$265.4147	$265.41	$265.40	$265.40
Purchase #6	$99.57	10.128%	$109.6544	$109.65	$109.65	$109.70
Purchase #7	$82.60	10.270%	$91.083	$91.08	$91.10	$91.10
7 purchase totals =	$962.05		$1,047.8731	$1,047.86	$1,047.85	$1,048.00