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	$189.41	3.711%	$196.439	$196.44	$196.45	$196.40
Purchase #2	$228.57	13.571%	$259.5892	$259.59	$259.60	$259.60
Purchase #3	$236.30	4.367%	$246.6192	$246.62	$246.60	$246.60
Purchase #4	$199.70	9.102%	$217.8767	$217.88	$217.90	$217.90
Purchase #5	$65.40	10.728%	$72.4161	$72.42	$72.40	$72.40
Purchase #6	$48.26	5.822%	$51.0697	$51.07	$51.05	$51.10
Purchase #7	$123.76	6.145%	$131.3651	$131.37	$131.35	$131.40
7 purchase totals =	$1,091.40		$1,175.3750	$1,175.39	$1,175.35	$1,175.40