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	$213.63	4.356%	$222.9357	$222.94	$222.95	$222.90
Purchase #2	$35.38	11.833%	$39.5665	$39.57	$39.55	$39.60
Purchase #3	$133.89	6.719%	$142.8861	$142.89	$142.90	$142.90
Purchase #4	$203.56	11.536%	$227.0427	$227.04	$227.05	$227.00
Purchase #5	$162.25	10.753%	$179.6967	$179.70	$179.70	$179.70
Purchase #6	$155.46	11.215%	$172.8948	$172.89	$172.90	$172.90
Purchase #7	$24.41	10.426%	$26.955	$26.96	$26.95	$27.00
7 purchase totals =	$928.58		$1,011.9775	$1,011.99	$1,012.00	$1,012.00