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	$236.35	10.789%	$261.8498	$261.85	$261.85	$261.80
Purchase #2	$89.63	3.287%	$92.5761	$92.58	$92.60	$92.60
Purchase #3	$53.83	10.759%	$59.6216	$59.62	$59.60	$59.60
Purchase #4	$201.97	12.276%	$226.7638	$226.76	$226.75	$226.80
Purchase #5	$53.65	3.224%	$55.3797	$55.38	$55.40	$55.40
Purchase #6	$6.64	7.505%	$7.1383	$7.14	$7.15	$7.10
Purchase #7	$186.62	11.538%	$208.1522	$208.15	$208.15	$208.20
7 purchase totals =	$828.69		$911.4815	$911.48	$911.50	$911.50