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	$61.47	3.286%	$63.4899	$63.49	$63.50	$63.50
Purchase #2	$20.50	3.337%	$21.1841	$21.18	$21.20	$21.20
Purchase #3	$66.63	11.866%	$74.5363	$74.54	$74.55	$74.50
Purchase #4	$152.36	9.618%	$167.014	$167.01	$167.00	$167.00
Purchase #5	$89.82	6.860%	$95.9817	$95.98	$96.00	$96.00
Purchase #6	$69.43	13.143%	$78.5552	$78.56	$78.55	$78.60
Purchase #7	$93.62	12.531%	$105.3515	$105.35	$105.35	$105.40
7 purchase totals =	$553.83		$606.1127	$606.11	$606.15	$606.20