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	$193.37	4.613%	$202.2902	$202.29	$202.30	$202.30
Purchase #2	$197.59	5.469%	$208.3962	$208.40	$208.40	$208.40
Purchase #3	$124.44	12.818%	$140.3907	$140.39	$140.40	$140.40
Purchase #4	$174.98	12.164%	$196.2646	$196.26	$196.25	$196.30
Purchase #5	$119.92	10.443%	$132.4432	$132.44	$132.45	$132.40
Purchase #6	$69.75	12.422%	$78.4143	$78.41	$78.40	$78.40
Purchase #7	$46.54	3.794%	$48.3057	$48.31	$48.30	$48.30
7 purchase totals =	$926.59		$1,006.5049	$1,006.50	$1,006.50	$1,006.50