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	$151.63	8.545%	$164.5868	$164.59	$164.60	$164.60
Purchase #2	$62.38	3.558%	$64.5995	$64.60	$64.60	$64.60
Purchase #3	$205.67	3.747%	$213.3765	$213.38	$213.40	$213.40
Purchase #4	$116.50	9.435%	$127.4918	$127.49	$127.50	$127.50
Purchase #5	$70.61	3.729%	$73.243	$73.24	$73.25	$73.20
Purchase #6	$188.45	11.300%	$209.7449	$209.74	$209.75	$209.70
Purchase #7	$87.31	12.856%	$98.5346	$98.53	$98.55	$98.50
7 purchase totals =	$882.55		$951.5771	$951.57	$951.65	$951.50