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	$210.52	12.631%	$237.1108	$237.11	$237.10	$237.10
Purchase #2	$142.82	8.863%	$155.4781	$155.48	$155.50	$155.50
Purchase #3	$34.78	7.269%	$37.3082	$37.31	$37.30	$37.30
Purchase #4	$240.70	12.176%	$270.0076	$270.01	$270.00	$270.00
Purchase #5	$101.35	9.378%	$110.8546	$110.85	$110.85	$110.90
Purchase #6	$51.69	7.377%	$55.5032	$55.50	$55.50	$55.50
Purchase #7	$179.25	5.176%	$188.528	$188.53	$188.55	$188.50
7 purchase totals =	$961.11		$1,054.7905	$1,054.79	$1,054.80	$1,054.80