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	$77.52	11.248%	$86.2394	$86.24	$86.25	$86.20
Purchase #2	$214.86	6.587%	$229.0128	$229.01	$229.00	$229.00
Purchase #3	$133.94	5.723%	$141.6054	$141.61	$141.60	$141.60
Purchase #4	$39.69	8.149%	$42.9243	$42.92	$42.90	$42.90
Purchase #5	$114.42	11.237%	$127.2774	$127.28	$127.30	$127.30
Purchase #6	$242.30	11.638%	$270.4989	$270.50	$270.50	$270.50
Purchase #7	$166.65	9.225%	$182.0235	$182.02	$182.00	$182.00
7 purchase totals =	$989.38		$1,079.5817	$1,079.58	$1,079.55	$1,079.50