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	$223.84	13.854%	$254.8508	$254.85	$254.85	$254.90
Purchase #2	$102.66	12.319%	$115.3067	$115.31	$115.30	$115.30
Purchase #3	$145.95	4.523%	$152.5513	$152.55	$152.55	$152.60
Purchase #4	$217.59	4.755%	$227.9364	$227.94	$227.95	$227.90
Purchase #5	$43.49	4.411%	$45.4083	$45.41	$45.40	$45.40
Purchase #6	$152.30	10.652%	$168.523	$168.52	$168.50	$168.50
Purchase #7	$122.37	8.802%	$133.141	$133.14	$133.15	$133.10
7 purchase totals =	$1,008.20		$1,097.7175	$1,097.72	$1,097.70	$1,097.70