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	$233.70	10.711%	$258.7316	$258.73	$258.75	$258.70
Purchase #2	$206.73	5.171%	$217.42	$217.42	$217.40	$217.40
Purchase #3	$115.35	13.549%	$130.9788	$130.98	$131.00	$131.00
Purchase #4	$112.32	3.468%	$116.2153	$116.22	$116.20	$116.20
Purchase #5	$181.96	12.484%	$204.6759	$204.68	$204.70	$204.70
Purchase #6	$169.79	9.189%	$185.392	$185.39	$185.40	$185.40
Purchase #7	$76.47	8.402%	$82.895	$82.90	$82.90	$82.90
7 purchase totals =	$1,096.32		$1,196.3086	$1,196.32	$1,196.35	$1,196.30