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	$208.57	12.113%	$233.8341	$233.83	$233.85	$233.80
Purchase #2	$164.60	7.519%	$176.9763	$176.98	$177.00	$177.00
Purchase #3	$28.90	7.755%	$31.1412	$31.14	$31.15	$31.10
Purchase #4	$78.76	13.333%	$89.2611	$89.26	$89.25	$89.30
Purchase #5	$121.27	8.449%	$131.5161	$131.52	$131.50	$131.50
Purchase #6	$249.60	7.584%	$268.5297	$268.53	$268.55	$268.50
Purchase #7	$66.89	8.665%	$72.686	$72.69	$72.70	$72.70
7 purchase totals =	$918.59		$1,003.9445	$1,003.95	$1,004.00	$1,003.90