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	$213.43	11.770%	$238.5507	$238.55	$238.55	$238.60
Purchase #2	$26.27	6.264%	$27.9156	$27.92	$27.90	$27.90
Purchase #3	$29.74	7.734%	$32.0401	$32.04	$32.05	$32.00
Purchase #4	$56.59	8.380%	$61.3322	$61.33	$61.35	$61.30
Purchase #5	$163.80	4.786%	$171.6395	$171.64	$171.65	$171.60
Purchase #6	$166.62	10.661%	$184.3834	$184.38	$184.40	$184.40
Purchase #7	$249.89	5.297%	$263.1267	$263.13	$263.15	$263.10
7 purchase totals =	$906.34		$978.9882	$978.99	$979.05	$978.90