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	$101.56	8.171%	$109.8585	$109.86	$109.85	$109.90
Purchase #2	$6.90	7.151%	$7.3934	$7.39	$7.40	$7.40
Purchase #3	$71.55	6.855%	$76.4548	$76.45	$76.45	$76.50
Purchase #4	$171.56	11.606%	$191.4713	$191.47	$191.45	$191.50
Purchase #5	$178.84	3.365%	$184.858	$184.86	$184.85	$184.90
Purchase #6	$93.67	10.375%	$103.3883	$103.39	$103.40	$103.40
Purchase #7	$171.69	8.675%	$186.5841	$186.58	$186.60	$186.60
7 purchase totals =	$795.77		$860.0084	$860.00	$860.00	$860.20