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	$140.85	7.193%	$150.9813	$150.98	$151.00	$151.00
Purchase #2	$36.50	11.356%	$40.6449	$40.64	$40.65	$40.60
Purchase #3	$74.84	4.664%	$78.3305	$78.33	$78.35	$78.30
Purchase #4	$238.52	9.549%	$261.2963	$261.30	$261.30	$261.30
Purchase #5	$143.34	5.312%	$150.9542	$150.95	$150.95	$151.00
Purchase #6	$213.25	9.449%	$233.4	$233.40	$233.40	$233.40
Purchase #7	$211.95	10.159%	$233.482	$233.48	$233.50	$233.50
7 purchase totals =	$1,059.25		$1,149.0892	$1,149.08	$1,149.15	$1,149.10