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	$154.75	6.162%	$164.2857	$164.29	$164.30	$164.30
Purchase #2	$217.91	9.241%	$238.0471	$238.05	$238.05	$238.00
Purchase #3	$91.53	7.666%	$98.5467	$98.55	$98.55	$98.50
Purchase #4	$189.89	5.551%	$200.4308	$200.43	$200.45	$200.40
Purchase #5	$100.88	8.357%	$109.3105	$109.31	$109.30	$109.30
Purchase #6	$113.98	6.355%	$121.2234	$121.22	$121.20	$121.20
Purchase #7	$242.87	4.554%	$253.9303	$253.93	$253.95	$253.90
7 purchase totals =	$1,111.81		$1,185.7745	$1,185.78	$1,185.80	$1,185.60