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	$112.71	9.449%	$123.36	$123.36	$123.35	$123.40
Purchase #2	$71.49	12.436%	$80.3805	$80.38	$80.40	$80.40
Purchase #3	$159.47	4.295%	$166.3192	$166.32	$166.30	$166.30
Purchase #4	$239.73	3.719%	$248.6456	$248.65	$248.65	$248.60
Purchase #5	$144.96	9.766%	$159.1168	$159.12	$159.10	$159.10
Purchase #6	$128.55	8.811%	$139.8765	$139.88	$139.90	$139.90
Purchase #7	$56.83	5.316%	$59.8511	$59.85	$59.85	$59.90
7 purchase totals =	$913.74		$977.5497	$977.56	$977.55	$977.60