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	$111.89	4.273%	$116.6711	$116.67	$116.65	$116.70
Purchase #2	$210.48	12.709%	$237.2299	$237.23	$237.25	$237.20
Purchase #3	$169.31	13.357%	$191.9247	$191.92	$191.90	$191.90
Purchase #4	$96.39	13.477%	$109.3805	$109.38	$109.40	$109.40
Purchase #5	$247.72	3.843%	$257.2399	$257.24	$257.25	$257.20
Purchase #6	$99.65	5.224%	$104.8557	$104.86	$104.85	$104.90
Purchase #7	$107.95	11.403%	$120.2595	$120.26	$120.25	$120.30
7 purchase totals =	$1,043.39		$1,137.5613	$1,137.56	$1,137.55	$1,137.60