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	$66.82	5.362%	$70.4029	$70.40	$70.40	$70.40
Purchase #2	$6.57	10.851%	$7.2829	$7.28	$7.30	$7.30
Purchase #3	$81.78	10.452%	$90.3276	$90.33	$90.35	$90.30
Purchase #4	$91.81	6.616%	$97.8841	$97.88	$97.90	$97.90
Purchase #5	$115.91	3.826%	$120.3447	$120.34	$120.35	$120.30
Purchase #6	$63.53	13.672%	$72.2158	$72.22	$72.20	$72.20
Purchase #7	$141.95	7.360%	$152.3975	$152.40	$152.40	$152.40
7 purchase totals =	$568.37		$610.8555	$610.85	$610.90	$610.80