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	$246.35	3.199%	$254.2307	$254.23	$254.25	$254.20
Purchase #2	$168.94	9.758%	$185.4252	$185.43	$185.45	$185.40
Purchase #3	$54.65	11.641%	$61.0118	$61.01	$61.00	$61.00
Purchase #4	$167.86	6.357%	$178.5309	$178.53	$178.55	$178.50
Purchase #5	$5.59	11.866%	$6.2533	$6.25	$6.25	$6.30
Purchase #6	$34.96	8.140%	$37.8057	$37.81	$37.80	$37.80
Purchase #7	$39.37	5.784%	$41.6472	$41.65	$41.65	$41.60
7 purchase totals =	$717.72		$764.9048	$764.91	$764.95	$764.80