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	$195.25	9.394%	$213.5918	$213.59	$213.60	$213.60
Purchase #2	$67.49	7.305%	$72.4201	$72.42	$72.40	$72.40
Purchase #3	$44.56	4.293%	$46.473	$46.47	$46.45	$46.50
Purchase #4	$145.26	7.683%	$156.4203	$156.42	$156.40	$156.40
Purchase #5	$81.78	11.682%	$91.3335	$91.33	$91.35	$91.30
Purchase #6	$14.54	4.598%	$15.2085	$15.21	$15.20	$15.20
Purchase #7	$139.86	8.298%	$151.4656	$151.47	$151.45	$151.50
7 purchase totals =	$688.74		$746.9128	$746.91	$746.85	$746.90