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	$105.91	3.707%	$109.8361	$109.84	$109.85	$109.80
Purchase #2	$82.86	8.678%	$90.0506	$90.05	$90.05	$90.10
Purchase #3	$91.38	8.571%	$99.2122	$99.21	$99.20	$99.20
Purchase #4	$203.75	11.475%	$227.1303	$227.13	$227.15	$227.10
Purchase #5	$161.26	11.265%	$179.4259	$179.43	$179.45	$179.40
Purchase #6	$189.85	12.808%	$214.166	$214.17	$214.15	$214.20
Purchase #7	$176.82	3.276%	$182.6126	$182.61	$182.60	$182.60
7 purchase totals =	$1,011.83		$1,102.4337	$1,102.44	$1,102.45	$1,102.40