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	$232.84	11.416%	$259.421	$259.42	$259.40	$259.40
Purchase #2	$184.88	5.253%	$194.5917	$194.59	$194.60	$194.60
Purchase #3	$236.42	10.753%	$261.8422	$261.84	$261.85	$261.80
Purchase #4	$119.75	4.812%	$125.5124	$125.51	$125.50	$125.50
Purchase #5	$40.66	7.204%	$43.5891	$43.59	$43.60	$43.60
Purchase #6	$86.34	3.169%	$89.0761	$89.08	$89.10	$89.10
Purchase #7	$72.95	12.841%	$82.3175	$82.32	$82.30	$82.30
7 purchase totals =	$973.84		$1,056.3500	$1,056.35	$1,056.35	$1,056.30