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	$160.86	12.626%	$181.1702	$181.17	$181.15	$181.20
Purchase #2	$146.30	3.250%	$151.0548	$151.05	$151.05	$151.10
Purchase #3	$53.31	12.355%	$59.8965	$59.90	$59.90	$59.90
Purchase #4	$202.71	7.143%	$217.1896	$217.19	$217.20	$217.20
Purchase #5	$162.75	9.657%	$178.4668	$178.47	$178.45	$178.50
Purchase #6	$124.64	5.227%	$131.1549	$131.15	$131.15	$131.20
Purchase #7	$117.76	6.147%	$124.9987	$125.00	$125.00	$125.00
7 purchase totals =	$968.33		$1,043.9315	$1,043.93	$1,043.90	$1,044.10