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	$23.93	8.204%	$25.8932	$25.89	$25.90	$25.90
Purchase #2	$194.35	4.571%	$203.2337	$203.23	$203.25	$203.20
Purchase #3	$142.39	6.663%	$151.8774	$151.88	$151.90	$151.90
Purchase #4	$139.89	8.337%	$151.5526	$151.55	$151.55	$151.60
Purchase #5	$102.56	8.767%	$111.5514	$111.55	$111.55	$111.60
Purchase #6	$185.87	8.131%	$200.9831	$200.98	$201.00	$201.00
Purchase #7	$198.73	6.430%	$211.5083	$211.51	$211.50	$211.50
7 purchase totals =	$987.72		$1,056.5997	$1,056.59	$1,056.65	$1,056.70