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	$231.31	10.334%	$255.2136	$255.21	$255.20	$255.20
Purchase #2	$88.40	8.462%	$95.8804	$95.88	$95.90	$95.90
Purchase #3	$38.88	5.716%	$41.1024	$41.10	$41.10	$41.10
Purchase #4	$188.40	5.259%	$198.308	$198.31	$198.30	$198.30
Purchase #5	$73.83	4.360%	$77.049	$77.05	$77.05	$77.00
Purchase #6	$166.50	13.265%	$188.5862	$188.59	$188.60	$188.60
Purchase #7	$67.28	7.613%	$72.402	$72.40	$72.40	$72.40
7 purchase totals =	$854.60		$928.5416	$928.54	$928.55	$928.50