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	$250.96	7.167%	$268.9463	$268.95	$268.95	$268.90
Purchase #2	$80.60	9.207%	$88.0208	$88.02	$88.00	$88.00
Purchase #3	$204.42	5.579%	$215.8246	$215.82	$215.80	$215.80
Purchase #4	$109.80	5.791%	$116.1585	$116.16	$116.15	$116.20
Purchase #5	$35.84	4.821%	$37.5678	$37.57	$37.55	$37.60
Purchase #6	$118.95	8.392%	$128.9323	$128.93	$128.95	$128.90
Purchase #7	$240.37	6.645%	$256.3426	$256.34	$256.35	$256.30
7 purchase totals =	$1,040.94		$1,111.7929	$1,111.79	$1,111.75	$1,111.70