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	$179.78	9.365%	$196.6164	$196.62	$196.60	$196.60
Purchase #2	$89.55	11.606%	$99.9432	$99.94	$99.95	$99.90
Purchase #3	$93.83	10.262%	$103.4588	$103.46	$103.45	$103.50
Purchase #4	$28.44	10.374%	$31.3904	$31.39	$31.40	$31.40
Purchase #5	$47.39	9.464%	$51.875	$51.88	$51.90	$51.90
Purchase #6	$187.97	13.650%	$213.6279	$213.63	$213.65	$213.60
Purchase #7	$164.44	12.739%	$185.388	$185.39	$185.40	$185.40
7 purchase totals =	$791.40		$882.2997	$882.31	$882.35	$882.30