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	$53.50	11.103%	$59.4401	$59.44	$59.45	$59.40
Purchase #2	$66.33	4.786%	$69.5046	$69.50	$69.50	$69.50
Purchase #3	$212.88	7.838%	$229.5655	$229.57	$229.55	$229.60
Purchase #4	$162.83	9.375%	$178.0953	$178.10	$178.10	$178.10
Purchase #5	$127.61	8.626%	$138.6176	$138.62	$138.60	$138.60
Purchase #6	$55.89	8.847%	$60.8346	$60.83	$60.85	$60.80
Purchase #7	$240.86	4.340%	$251.3133	$251.31	$251.30	$251.30
7 purchase totals =	$919.90		$987.3710	$987.37	$987.35	$987.30