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	$41.94	4.152%	$43.6813	$43.68	$43.70	$43.70
Purchase #2	$166.44	7.711%	$179.2742	$179.27	$179.25	$179.30
Purchase #3	$162.91	5.526%	$171.9124	$171.91	$171.90	$171.90
Purchase #4	$248.90	8.677%	$270.4971	$270.50	$270.50	$270.50
Purchase #5	$219.78	9.107%	$239.7954	$239.80	$239.80	$239.80
Purchase #6	$127.37	9.524%	$139.5007	$139.50	$139.50	$139.50
Purchase #7	$38.60	10.697%	$42.729	$42.73	$42.75	$42.70
7 purchase totals =	$1,005.94		$1,087.3901	$1,087.39	$1,087.40	$1,087.40