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	$164.87	10.154%	$181.6109	$181.61	$181.60	$181.60
Purchase #2	$37.52	9.848%	$41.215	$41.22	$41.20	$41.20
Purchase #3	$79.74	12.339%	$89.5791	$89.58	$89.60	$89.60
Purchase #4	$19.90	9.294%	$21.7495	$21.75	$21.75	$21.70
Purchase #5	$241.45	6.622%	$257.4388	$257.44	$257.45	$257.40
Purchase #6	$42.40	6.199%	$45.0284	$45.03	$45.05	$45.00
Purchase #7	$73.75	3.586%	$76.3947	$76.39	$76.40	$76.40
7 purchase totals =	$659.63		$713.0164	$713.02	$713.05	$712.90