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	$39.67	5.517%	$41.8586	$41.86	$41.85	$41.90
Purchase #2	$84.65	5.165%	$89.0222	$89.02	$89.00	$89.00
Purchase #3	$92.62	9.830%	$101.7245	$101.72	$101.70	$101.70
Purchase #4	$236.39	6.760%	$252.37	$252.37	$252.35	$252.40
Purchase #5	$154.53	6.734%	$164.9361	$164.94	$164.95	$164.90
Purchase #6	$190.69	9.377%	$208.571	$208.57	$208.55	$208.60
Purchase #7	$215.59	11.497%	$240.3764	$240.38	$240.40	$240.40
7 purchase totals =	$1,014.14		$1,098.8588	$1,098.86	$1,098.80	$1,098.90