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	$60.32	11.802%	$67.439	$67.44	$67.45	$67.40
Purchase #2	$77.73	5.342%	$81.8823	$81.88	$81.90	$81.90
Purchase #3	$179.27	4.677%	$187.6545	$187.65	$187.65	$187.70
Purchase #4	$177.83	6.793%	$189.91	$189.91	$189.90	$189.90
Purchase #5	$28.53	10.151%	$31.4261	$31.43	$31.45	$31.40
Purchase #6	$201.28	7.242%	$215.8567	$215.86	$215.85	$215.90
Purchase #7	$226.63	4.867%	$237.6601	$237.66	$237.65	$237.70
7 purchase totals =	$951.59		$1,011.8287	$1,011.83	$1,011.85	$1,011.90