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	$89.89	4.728%	$94.14	$94.14	$94.15	$94.10
Purchase #2	$97.96	12.188%	$109.8994	$109.90	$109.90	$109.90
Purchase #3	$220.78	8.675%	$239.9327	$239.93	$239.95	$239.90
Purchase #4	$243.95	12.239%	$273.807	$273.81	$273.80	$273.80
Purchase #5	$141.55	4.824%	$148.3784	$148.38	$148.40	$148.40
Purchase #6	$55.55	10.510%	$61.3883	$61.39	$61.40	$61.40
Purchase #7	$121.58	5.696%	$128.5052	$128.51	$128.50	$128.50
7 purchase totals =	$971.26		$1,056.0510	$1,056.06	$1,056.10	$1,056.00