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	$38.61	6.682%	$41.1899	$41.19	$41.20	$41.20
Purchase #2	$225.44	11.729%	$251.8819	$251.88	$251.90	$251.90
Purchase #3	$65.79	8.237%	$71.2091	$71.21	$71.20	$71.20
Purchase #4	$40.64	6.520%	$43.2897	$43.29	$43.30	$43.30
Purchase #5	$72.78	8.342%	$78.8513	$78.85	$78.85	$78.90
Purchase #6	$67.76	13.299%	$76.7714	$76.77	$76.75	$76.80
Purchase #7	$49.41	7.626%	$53.178	$53.18	$53.20	$53.20
7 purchase totals =	$560.43		$616.3713	$616.37	$616.40	$616.50