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	$96.67	5.764%	$102.2421	$102.24	$102.25	$102.20
Purchase #2	$138.27	3.339%	$142.8868	$142.89	$142.90	$142.90
Purchase #3	$131.68	7.418%	$141.448	$141.45	$141.45	$141.40
Purchase #4	$96.39	8.452%	$104.5369	$104.54	$104.55	$104.50
Purchase #5	$105.77	6.719%	$112.8767	$112.88	$112.90	$112.90
Purchase #6	$205.42	4.840%	$215.3623	$215.36	$215.35	$215.40
Purchase #7	$67.91	7.526%	$73.0209	$73.02	$73.00	$73.00
7 purchase totals =	$842.11		$892.3737	$892.38	$892.40	$892.30