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	$86.71	4.725%	$90.807	$90.81	$90.80	$90.80
Purchase #2	$179.46	3.187%	$185.1794	$185.18	$185.20	$185.20
Purchase #3	$157.77	10.462%	$174.2759	$174.28	$174.30	$174.30
Purchase #4	$145.28	4.523%	$151.851	$151.85	$151.85	$151.90
Purchase #5	$19.40	10.454%	$21.4281	$21.43	$21.45	$21.40
Purchase #6	$165.53	12.838%	$186.7807	$186.78	$186.80	$186.80
Purchase #7	$218.69	6.466%	$232.8305	$232.83	$232.85	$232.80
7 purchase totals =	$972.84		$1,043.1526	$1,043.16	$1,043.25	$1,043.20