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	$147.70	6.605%	$157.4556	$157.46	$157.45	$157.50
Purchase #2	$128.78	8.647%	$139.9156	$139.92	$139.90	$139.90
Purchase #3	$142.63	5.820%	$150.9311	$150.93	$150.95	$150.90
Purchase #4	$100.61	4.688%	$105.3266	$105.33	$105.35	$105.30
Purchase #5	$42.26	9.807%	$46.4044	$46.40	$46.40	$46.40
Purchase #6	$39.46	6.347%	$41.9645	$41.96	$41.95	$42.00
Purchase #7	$60.81	12.498%	$68.41	$68.41	$68.40	$68.40
7 purchase totals =	$662.25		$710.4078	$710.41	$710.40	$710.40