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	$218.42	4.133%	$227.4473	$227.45	$227.45	$227.40
Purchase #2	$213.88	12.594%	$240.816	$240.82	$240.80	$240.80
Purchase #3	$64.97	3.410%	$67.1855	$67.19	$67.20	$67.20
Purchase #4	$42.67	6.726%	$45.54	$45.54	$45.55	$45.50
Purchase #5	$244.43	4.866%	$256.324	$256.32	$256.30	$256.30
Purchase #6	$71.86	13.638%	$81.6603	$81.66	$81.65	$81.70
Purchase #7	$37.98	6.361%	$40.3959	$40.40	$40.40	$40.40
7 purchase totals =	$894.21		$959.3690	$959.38	$959.35	$959.30