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	$200.41	7.501%	$215.4428	$215.44	$215.45	$215.40
Purchase #2	$241.61	9.486%	$264.5291	$264.53	$264.55	$264.50
Purchase #3	$119.87	10.392%	$132.3269	$132.33	$132.35	$132.30
Purchase #4	$157.32	3.564%	$162.9269	$162.93	$162.95	$162.90
Purchase #5	$244.97	8.348%	$265.4201	$265.42	$265.40	$265.40
Purchase #6	$162.57	10.611%	$179.8203	$179.82	$179.80	$179.80
Purchase #7	$38.48	6.106%	$40.8296	$40.83	$40.85	$40.80
7 purchase totals =	$1,165.23		$1,261.2957	$1,261.30	$1,261.35	$1,261.10