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	$67.33	6.724%	$71.8573	$71.86	$71.85	$71.90
Purchase #2	$119.35	11.435%	$132.9977	$133.00	$133.00	$133.00
Purchase #3	$233.69	13.579%	$265.4228	$265.42	$265.40	$265.40
Purchase #4	$59.91	7.176%	$64.2091	$64.21	$64.20	$64.20
Purchase #5	$59.36	13.567%	$67.4134	$67.41	$67.40	$67.40
Purchase #6	$90.39	10.107%	$99.5257	$99.53	$99.55	$99.50
Purchase #7	$224.26	3.595%	$232.3221	$232.32	$232.30	$232.30
7 purchase totals =	$854.29		$933.7481	$933.75	$933.70	$933.70